northern rampart, which also guarded the canal that supplied water to the city's centre. From the main gate, a street ran southwards in a straight line along the base of the acropolis and continued through the lower city to the southern riverbank – a distance of about . Apart from the southern zone, which housed large dwellings organised in three blocks, the lower town was unplanned; this distinguishes Ai-Khanoum from other Hellenistic foundations of the Near East, such as Seleucia on the Tigris, which tended to be built according to the Hippodamian grid plan. It was also the subject of a major redevelopment during the early second century BC, which resulted in slight disunity of the orientations of some major buildings (the palace, for example, is at an angle to the older main street). Ai-Khanoum was built predominantly using unbaked bricks, with baked bricks and stone used much less often. Palace complex The palace complex was large, measuring about , and occupying around a third of the lower town. The size and intricacy of the complex, which was built on the order of Eucratides I, would have served as a demonstration of the ruler's power and wealth; Bernard commented that it "simultaneously served three functions: it was a state structure, a residence, and a treasury". A huge plaza, in area, lay to the south of the palace and may have been used for military parades, drills, or simply as garrison quarters. The palace itself was accessed through a gateway known as the Main Propylaea, which opened on the west side of the main street; the propylaea itself had been built by an earlier ruler and was reconstructed under Eucratides. Encompassing a wide portico in between two adjoining porches, the roof of the structure was noted for its palmette antefixes. It allowed access to a curved road that ran towards the palace's courtyard. This rectangular courtyard, which measured and served as the main entrance to the palace, was entered from the curved road through another propylaeum. The courtyard was bordered by 118 Corinthian columns. The columns of the north, east, and west colonnades were high, while those of the south colonnade were almost tall, forming a Rhodian peristyle. The palace was entered through a hypostyle behind the southern portico; this vestibule, similar in style to a Persian iwan, was supported by eighteen columns, ornamented slightly differently from those in the courtyard.