The Propylaia () is the classical Greek Doric building complex that functioned as the monumental ceremonial gateway to the Acropolis of Athens. Built between 437 and 432 BCE as a part of the Periklean Building Program, it was the last in a series of gatehouses built on the citadel. Its architect was Mnesikles, his only known building. It is evident from traces left on the extant building that the plan for the Propylaia evolved considerably during its construction, and that the project was ultimately abandoned in an unfinished state.
History
The approach to the Acropolis is determined by its geography. The only accessible pathway to the plateau lies between what is now the bastion of the Temple of Athena Nike and the terrace of the Agrippa Monument. In Mycenaean times the bastion (also referred to as the pyrgos or tower) was encased in a cyclopean wall, and amongst the few Mycenaean structures left in the archaeological record is a substantial wall on the terrace of the bastion that was part of the system of fortifications of the Acropolis. This wall must have terminated at the first gateway, though opinions differ on the reconstruction of this earliest entrance. At some point in the archaic period a ramp replaced the bedrock pathway; the buttress wall on the north side of the existing stairway is from this period. This was followed shortly after Marathon by a programme of renovation on the Acropolis including the replacement of the gateway with a ceremonial entrance, usually referred to as the Older Propylon, and the refurbishment of the forecourt in front of it. At this time, a section of the western Bronze Age wall, south of the gateway, received a marble lining on its western face and an integrated base at the northern extent for a perirrhanterion, or lustral basin. Bundgaard identified several remnants of this propylon and postulated a significant gatehouse situated between the Mycenaean wall and the archaic apsidal structure known as Building B. What is evident, however, is that if the archaic gatehouse was not destroyed in the Persian attack of 480 then it must surely have been dismantled to facilitate the building works later in the century.
Mnesikles was appointed architect of the new propylon in 438. From traces left in the construction of the final building it has been possible to reconstruct the development of the building plans during its construction. It was the practice of Greek builders to prepare for the bonding of joining walls, roof timber and other features in advance of the following phase of construction. From the socket for the roof beam and the spur walls on the north and south flanks of the central hall it can be discerned that the original plan was for a much larger building than its final form. Mnesikles had planned a gatehouse composed of five halls: a central hall that would be the processional route to the Acropolis, two perpendicular flanking halls - north and south of the central hall - that would have spanned the whole width of the western end of the plateau, and two further, eastward projecting halls that were at 90 degrees to the north-south halls. Of these only the central hall, the north-east hall (the Pinakotheke) and a truncated version of the south-east hall reached completion. Furthermore, it is evident from the adaption of the stylobate that a stepped platform was added to the interior of the central hall such that the western-most tympanum and roof were raised above the rest of the building. The reasons for these alterations have been the cause of much speculation. They include practical considerations of the site, religious objections to the displacement of the adjoining shrines, and cost. Whatever the reason it is clear that the project was abandoned in an unfinished state in 432 with the lifting bosses remaining and the surface of the ashlar blocks left undressed.
Alterations to the Propylaia in the classical period were slight, the most significant being the construction of a monumental stairway in pentelic marble built in the reign of Claudius, probably 42 CE, and arranged as a straight flight of steps. This included a central inclined plane along which the sacrificial animals could be led, also a small dog-leg stairway on the Nike bastion that led to the Temple of Athena Nike. This project was supervised by the Athenian Tib. Claudius Novius, and is assumed to have been an Imperial benefaction from the great expense that must have been occurred.