In 267 CE, a Germanic people called the Heruli sacked Athens, and the city never quite trusted its safety again. In the aftermath the Athenians threw up the Post-Herulian Wall, a hasty fortification ringing the Acropolis, and the Beulé Gate was built into it. The change was profound. For a thousand years the Acropolis had been a sanctuary, a place of temples and processions. Now it became, in one scholar's phrase, 'a fortress with temples' - a defensive position bristling against invaders rather than a holy precinct open to pilgrims. The gate marks that turning point in stone, the moment sacred ground hardened into a stronghold.

The builders were in no mood to quarry fresh marble. Instead they dismantled the Choragic Monument of Nikias, a small temple-like structure erected around 320 BCE to celebrate an Athenian's victory in the city's dramatic competitions, and reassembled its pieces into the gate. The masons even numbered some blocks before pulling them down, so they could be slotted back together correctly. Nikias's original dedication inscription still runs across the gate's entablature, marooned far from the building it once honored. Because that monument had itself imitated the Acropolis gateway it now guarded, one historian called the result a 'twice-told Classicism' - an echo of an echo, ancient Athens quoting itself.

The gate served as the Acropolis's main entrance for centuries, gaining a wooden roof, a lowered lintel under the emperor Justinian, and extra storeys in Byzantine times. After the Fourth Crusade carved up the Byzantine Empire in 1204, Frankish lords took Athens and refortified the rock, eventually closing the gate off entirely. The Ottomans heightened its towers and piled a bastion on top. Layer accumulated on layer until the original gateway vanished from view and then from memory. By the nineteenth century, knowledge of the gate's existence had been lost completely - swallowed by the very fortifications meant to protect it.

In 1852 a young French archaeologist named Charles Ernest Beulé, working under the Greek antiquities chief Kyriakos Pittakis, became convinced a hidden gateway lay beneath the Ottoman bastion. He dug, and he found it. When his crews hit a block of mortar too stubborn for their tools, Beulé did something that scandalized his colleagues: he obtained gunpowder from French naval sailors patrolling the Aegean and blasted straight through it. Pittakis, watching, was nearly killed when flying debris pierced his hat, and rumors briefly spread that he had died. Greek newspapers, one of which had accused Beulé of wanting to blow up the whole Acropolis, were furious. But the gate emerged into daylight, and the discovery made Beulé's reputation. He even bolted a self-congratulatory inscription beside the entrance - a gesture a rival called 'an example of petty national and personal vanity.' The gate has carried his name ever since.

Beulé got one thing wrong: he believed his gate was the Acropolis's original classical entrance, designed by the architect of the Propylaia. Later scholars corrected him, dating it firmly to the late Roman period after the Herulian sack. The error did nothing to diminish the find. Today the Beulé Gate stands restored to a quieter duty. Since the 1960s the main entrance to the Acropolis has moved to the southeast, and the gate now serves chiefly as an exit - the threshold through which a day's worth of visitors descends from the Parthenon, back down the marble stair, beneath an inscription stolen from a forgotten monument, and out into the modern city.