The architect Mnesikles, identified by Plutarch as the man behind the Erechtheion, took up the gateway commission in 438 BC. His original design was wildly ambitious: five connected halls, two of them spanning the entire western edge of the plateau, two more projecting eastward at right angles. Only the central hall, the northeast wing called the Pinakotheke, and a stunted version of the southeast hall ever rose. The reasons remain debated. Religious objections may have arisen over displacing the adjoining shrines of Athena Nike and Artemis Brauronia. The terrain itself fought back. Money ran short. Whatever combination of forces it was, the building stopped being built, and the marks of that stopping are visible in every undressed surface.

Approached from the west, the central hall presents a hexastyle Doric front, six columns spaced with the central gap one triglyph wider than the rest, framing the processional route. Walk under that frieze and the architecture changes order: a double row of Ionic columns lines the passageway, their capitals turned to face you as you climb. The crepidoma uses Pentelic marble, but the bottom course and the orthostates switch to dark blue Eleusinian limestone, a deliberate ribbon of contrasting color at the building's base. The coffered ceiling, supported by marble beams six meters long, was painted with golden stars on a deep blue field. Most of that pigment is gone. The building proportions, like the Parthenon's, follow a careful ratio, 3:7 here against 4:9 there, paired buildings designed to speak the same architectural language.

Pausanias, walking through the Acropolis in the second century AD, paused inside the northeast wing and noted the paintings on its walls. Achilles among the women on Skyros. Diomedes and Odysseus stealing the Palladion from Troy. Two panels donated by Alkibiades to commemorate his Olympic chariot victories. Modern writers picked up the room's nickname, the Pinakotheke, and ran with it, but no ancient source ever called the building a picture gallery by intent. John Travlos noticed something else: the asymmetric door and windows match the layout of Greek dining rooms. Seventeen banqueting couches would fit end-to-end around the walls. The wing may have been built to feed Athens' magistrates after Panathenaic sacrifices, with paintings hung as decoration much later.

After classical Athens, the Propylaea kept living. The Romans laid a monumental marble stairway in 42 AD, with a central ramp gentle enough for sacrificial animals. The Byzantines walled in the south wing as a chapel and converted the central hall into a church dedicated to the Taxiarches. Justinian's engineers tucked a cistern between the wings. When the Frankish lords of the Duchy of Athens arrived in the thirteenth century, they turned the whole complex into a fortified residence, a Levantine-style crusader keep with a tall tower added on the south wing. Then came the Ottomans, and the gateway suffered the fate it might have predicted: it became a powder magazine. The damage from those centuries was severe enough that nineteenth-century archaeologists spent decades simply pulling apart what had accreted, before Nikolaos Balanos began the major restoration work between 1909 and 1917.

Demosthenes, writing in the fourth century BC, called the Propylaea a monument equal to the Parthenon, built by the men who beat the Persians at Salamis. Cicero, writing centuries later, complained that it had cost too much. Both responses survive in the building's afterlife. The Greater Propylaea at Eleusis, commissioned by Hadrian in the second century, copied the central hall almost exactly. In 1791, Carl Gotthard Langhans drew on French engravings of the Athenian original to design Berlin's Brandenburg Gate, launching the Greek Revival in Germany. The unfinished gateway became the template for monumental thresholds, copied as if it had always been complete. Stand on the Mnesiklean ramp at sunset, and the building still works the way it was meant to: a transition, a ceremonial slowing of pace, a marble framing of the climb toward what lies beyond.