OPINION OF THE COURT
FLAHERTY, Justice.Appellant, Mary Finn, was awarded a judgment in the amount of $203,500 against appellee, City of Philadelphia, after appellant was injured when she fell on a grease-covered city sidewalk. The Commonwealth Court reversed the judgment due to governmental immunity under the Political Subdivision Tort Claims Act, 42 Pa.C.S. §§ 8541-8564, holding that the “sidewalk exception,” 42 Pa.C.S. § 8542(b)(7), did not pierce the city’s immunity in this case. We granted allocatur to clarify precedents of this court relating to immunity, and to construe the language of the sidewalk exception to governmental immunity.
This case arises from the following background. After dark on the evening of December 24, 1987, appellant was walking on the sidewalk adjacent to city-owned property on Vine *599Street in Philadelphia, when she slipped on an accumulation of grease. Her fall caused serious injury, and she brought a personal injury action against the city. The city raised the defense of governmental immunity under the tort claims act, moving for summary judgment, which was denied, and the case was tried on stipulated facts. Judgment was entered for appellant in the stipulated amount of $203,500.
On appeal, the Commonwealth Court reversed, holding that an accumulation of grease on a sidewalk is not “a dangerous condition of sidewalks,” 42 Pa.C.S. § 8542(b)(7), the statutory requisite to circumventing the city’s governmental immunity and permitting tort liability.
The gist of appellant’s argument is that the greasy condition of the sidewalk which caused her injury is embraced within the statutory exception to the governmental immunity created by the Political Subdivision Tort Claims Act; she argues that in the language of the act, the grease constituted a dangerous condition of the sidewalk. It would be erroneous, in this view, to focus on the word “of,” in contradistinction to the word “on”; rather, the emphasis should be on “dangerous condition” and an analysis of what the legislature meant by that term. She relies heavily on Bendas v. Township of White Deer, 531 Pa. 180, 611 A.2d 1184 (1992).
Appellee’s argument emphasizes the principle that exceptions to governmental immunity must be strictly construed. The city stresses this court’s holding in Snyder v. Harmon, 522 Pa. 424, 562 A.2d 307 (1989), to the effect that claims involving government property must establish an artificial condition or defect of the property itself, and that an actionable dangerous condition of government property must derive, originate from, or have as its source the property in question and may not arise from a source outside the property. The city argues that because grease does not derive or originate from the sidewalk, it is not a defect of the sidewalk itself; therefore, as a matter of law, grease cannot be considered a dangerous condition of the sidewalk. Hence it does not satisfy the statutory sidewalk exception to the doctrine of governmen*600tal immunity and the Commonwealth Court was correct in reversing the judgment against the city.
It is evident that this case turns on the meaning of the sidewalk exception to the tort claims act. 42 Pa.C.S. § 8542(b)(7) states:
(b) Acts which may impose liability. — The following acts by a local agency or any of its employees may result in the imposition of liability on a local agency:
(7) Sidewalks. — A dangerous condition of sidewalks within the rights-of-way of streets owned by the local agency, except that the claimant to recover must establish that the dangerous condition created a reasonably foreseeable risk of the kind of injury which was incurred and that the local agency had actual notice or could reasonably be charged with notice under the circumstances of the dangerous condition at a sufficient time prior to the event to have taken measures to protect against the dangerous condition. When a local agency is hable for damages under this paragraph by reason of its power and authority to require installation and repair of sidewalks under the care, custody and control of other persons, the local agency shall be secondarily hable only and such other persons shall be primarily hable.
To apply this language to this case, we think it helpful to review the precedents which guide our decision.
In Mascaro v. Youth Study Center, 514 Pa. 351, 523 A.2d 1118 (1987), and Snyder v. Harmon, supra, at 424, 562 A.2d 307, we reviewed the origin of the legislation and the principles governing its interpretation. Mascaro provides the following history: In response to our abrogation of the judicially-created doctrine of governmental immunity in Ayala v. Philadelphia Bd. of Public Education, 453 Pa. 584, 305 A.2d 877 (1973), the legislature enacted the Pohtical Subdivision Tort Claims Act, 42 Pa.C.S. '§§ 8541-8564. The act legislatively raises the shield of governmental immunity against any damages on account of personal injury or property damage caused by any act of a local agency or employee thereof, except as *601otherwise provided in 42 Pa.C.S. § 8542. Mascaro, 514 Pa. at 355, 523 A.2d at 1123. Snyder provides a strikingly similar history pertaining to sovereign immunity. In Mayle v. Pennsylvania Dep’t of Highways, 479 Pa. 384, 388 A.2d 709 (1978), we abrogated the doctrine of sovereign immunity. In response, the legislature enacted the Sovereign Immunity Act, 42 Pa.C.S. § 8521 el seq. The act reinstated the doctrine of sovereign immunity, limiting the instances in which an individual may sue the Commonwealth to a set of specific situations enumerated in 42 Pa.C.S. § 8522. Snyder, 522 Pa. at 431, 562 A.2d at 310-11.
Because the legislature’s intent was to provide immunities, we have held that the exceptions to immunity must be strictly construed. Id. at 433, 434, 562 A.2d at 311, 312; Mascaro, 514 Pa. at 361, 523 A.2d at 1123; Kiley by Kiley v. City of Philadelphia, 537 Pa. 502, 506, 645 A.2d 184, 185-86 (1994). Moreover, this court has held that the two statutes dealing with governmental and sovereign immunities, viz., the Political Subdivision Tort Claims Act and the Sovereign Immunity Act, are to be interpreted consistently, as they deal with indistinguishable subject matter. Id. at 507, 645 A.2d at 186; Crowell v. City of Philadelphia, 531 Pa. 400, 410 n. 8, 613 A.2d 1178, 1182 n. 8 (1992); Snyder, 522 Pa. at 435 n. 7, 562 A.2d at 312 n. 7.
Within those very general guidelines, this court has decided cases involving the real estate and sidewalk exceptions which provide more specific guidance for the question presented in this case, that is, whether an accumulation of grease on a sidewalk is a dangerous condition of the sidewalk. In Snyder v. Harmon, supra, at 424, 562 A.2d 307, we construed the words “[a] dangerous condition of Commonwealth agency real estate” as follows: “These key words indicate that a dangerous condition must derive, originate from or have as its source the Commonwealth realty.” Snyder, 522 Pa. at 433, 562 A.2d at 311. “[Tjhere must be negligence which makes the real property itself unsafe for activities for which it is used.” Id. at 434, 562 A.2d at 312. Mascaro, supra, at 351, 523 A.2d 1118, reiterated this rule: ‘We ... hold that the real estate exception can be applied only to those cases where it is alleged *602that the artificial condition or defect of the land itself causes the injury, not merely when it facilitates the injury by the acts of others, whose acts are outside the statute’s scope of liability.” 514 Pa. at 363, 523 A.2d at 1124 (emphasis in original). And again, “We have consistently maintained our view that the focus of the negligent act involving a use of government owned or controlled land (including streets and sidewalks) must be the actual defect of the land itself and that the rule of immunity can be waived only in those cases where it is alleged that the artificial condition or defect of the land itself causes the injury.” Kiley by Kiley, supra, 537 Pa. at 508, 645 A.2d at 187.
This interpretation is supported by the context of the “dangerous condition of sidewalks” requirement. The next sentence in the statute sheds light on what the legislature meant by “dangerous condition of sidewalks.” In distinguishing situations creating either primary or secondary liability of a governmental agency, the negligence of the agency relates to “installation and repair of sidewalks.” Installation and repair refer to the physical condition of the sidewalks themselves; by contrast, objects and substances upon sidewalks are not part of the physical condition of the sidewalks themselves. The language used in this section of the statute thus affords no basis to assert that foreign matter on sidewalks might result in governmental liability.
This much-litigated legislation has spawned other opinions which are less closely related to the present case but have nevertheless been cited. Appellant argues that Bendas v. Township of White Deer, supra, at 531 Pa. 180, 611 A.2d 1184, would permit the city to be held liable in tort. Moreover, the Commonwealth Court noted apparent inconsistency between Bendas and Mascaro, supra, at 514 Pa. 351, 523 A.2d 1118 and Snyder, supra, at 522 Pa. 424, 562 A.2d 307. We therefore review those decisions to clarify their holdings and their application to this case.
In Bendas, the court considered two issues: the first was “whether the Department [of Transportation] has a duty to make its highways safe for their intended purpose;” the second was “whether the failure of the Department to exercise *603that duty is actionable under an exception to the Sovereign Immunity Act.” 531 Pa. at 183, 611 A.2d at 1186. We cited Snyder, supra, in deciding that the Commonwealth agency had a clear duty to make its property safe for the activities for which it is regularly used. Id. The court found the second question more difficult, since a Commonwealth agency might breach a duty “yet not be liable unless the breach is coincidental with an exception to the Act.” Id. The exception applicable in Bendas was that of 42 Pa.C.S. § 8522(b)(4) which permits liability for a “dangerous condition of ... real estate and sidewalks ... and highways.... ” We held that when the Commonwealth agency or subdivision has a legal duty, the question of what is a dangerous condition is one of fact which must be answered by the jury, noting that a court is not precluded from entering judgment for the Commonwealth agency or subdivision when the facts establish as a matter of law that a dangerous condition did not exist. Id. at 185 n. 6, 611 A.2d at 1187 n. 6.
Mascaro involved a detainee at the defendant youth detention center who had a history of violent criminal assaults, then escaped and terrorized the Mascaro family, with tragic results. The Mascaros sued the political subdivision under the real estate exception to the governmental immunity act, 42 Pa.C.S. § 8542(b)(3), alleging negligent maintenance of the detention center which permitted the detainee to escape. The court held that the real estate exception “can be applied only to those cases where it is alleged that the artificial defect of the land itself causes the injury, not merely when it facilitates the injury by the acts of others, whose acts are outside the statute’s scope of liability.” 514 Pa. at 363, 523 A.2d at 1124. Thus, Mascaro is an example of a situation in which the political subdivision was not liable as a matter of law because the dangerous condition of the real estate itself did not cause the injury.
Snyder was a case in which travellers’ falls from the berm of a Commonwealth highway into a mine resulted in injuries and death, allegedly due to the Commonwealth agency’s negligent failure to maintain a safe roadway and to provide ade*604quate notice of a dangerous condition; the plaintiffs relied on the real estate exception to the Sovereign Immunity Act, 42 Pa.C.S. § 8522(b)(4). The court held that the statutory language unambiguously required that “a dangerous condition must derive, originate from or have as its source the Commonwealth realty,” 522 Pa. at 433, 562 A.2d at 311; that “there must be negligence which makes the real property itself unsafe for activities for which it is used,” id. at 434, 562 A.2d at 312; and that the real estate exception to the rule of immunity applies only when “it is alleged that the artificial condition or defect of the land itself causes an injury to occur,” id. at 434-35, 562 A.2d at 312.
In Ambacher v. Penrose, 92 Pa.Cmwlth. 401, 403-04, 499 A.2d 716, 717 (1985), and Ziccardi v. School District of Philadelphia, 91 Pa.Cmwlth. 595, 599, 498 A.2d 452, 454 (1985), the Commonwealth Court correctly applied this rule in determining that neither a wire fence which fell on a sidewalk nor a criminal assault on a city sidewalk was a dangerous condition “of the sidewalk.” Recent decisions of the Commonwealth Court indicate that that tribunal now consistently applies the rule in this way. In DeLuca v. School District of Philadelphia, 654 A.2d 29 (Pa.Cmwlth.1994), the court reviewed the claim of a student injured in a fall on a school sidewalk. The fall was caused by milk which had seeped from a trash bag placed next to the sidewalk by school employees and then frozen. The court held: “Because milk that has leaked onto a concrete pavement does not constitute a defect of the pavement itself, ... the School District was not liable under [42 Pa.C.S. §] 8542(b)(3) for the DeLucas’ injuries.” Id. at -, 654 A.2d at 31. In Shedrick v. William Penn School District, 654 A.2d 163 (Pa.Cmwlth.1995), the court reviewed a similar claim by a person injured when she fell in a high school where rainwater tracked indoors had caused the terrazzo floors to become slippery. She fell on a portion of the building’s floor not covered by mats although the custodian had mopped and laid mats in an attempt to keep the floors dry. The Commonwealth Court affirmed the trial court because the “rainwater on the floor of the high school neither derived nor originated *605from the School District’s real property, and no evidence was offered to establish that the floor itself was defective.” Id. at -, 654 A.2d at 165.
The common theme of all these cases is that liability depends, first, on the legal determination that an injury was caused by a condition of government realty itself, deriving, originating from, or having the realty as its source, and, only then, the factual determination that the condition was dangerous.
What is necessary, therefore, to pierce the Commonwealth agency’s immunity is proof of a defect of the sidewalk itself. Such proof might include an improperly designed sidewalk, an improperly constructed sidewalk, or a badly maintained, deteriorating, crumbling sidewalk. Here, however, we have no such allegation or proof. We have a perfectly designed and constructed sidewalk, undamaged, upon which an unidentified individual or individuals deposited a foreign substance which caused appellant’s injury. In the terms of Snyder, supra, at 522 Pa. 424, 562 A.2d 307, the dangerous condition did not derive, originate from or have as its source the sidewalk. In the language of the statutory exception to governmental immunity, the dangerous condition was on the sidewalk, not of the sidewalk, and thus is insufficient to create liability in the city.
We hold, therefore, that the Commonwealth Court correctly interpreted and applied the statute of governmental immunity, and thus affirm the judgment of the court.
Judgment affirmed.
ZAPPALA and CAPPY, JJ., file a dissenting opinion.
MONTEMURO, J., is sitting by designation.