Open Cistern of the Hebdomon (Fildamı)

Open Cistern of the Hebdomon
Fildamı

The open cistern near the Hebdomon was a huge Late Antique open-air water reservoir outside the city walls of Constantinople. It was located north of the Hebdomon (modern Bakırköy), a coastal suburb of Constantinople. This reservoir likely supplied water to the military camp and an imperial palace of the Hebdomon. It perhaps dates to the first half of the seventh century. Its Turkish name Fildamı (“Elephant Stables”) derives from a tradition of elephants being kept there. It later functioned as a “sunken” vegetable garden (Turkish çukurbostan) by the Ottoman era. It is now a park.

History

Fildamı, the large open reservoir north of the Hebdomon (modern Bakırköy), cannot be attested in any surviving texts. Unlike the other Byzantine open cisterns, it is located outside the city walls around 1.5 km from the northern shore of the Marmara Sea. It was built into the hill on the west side of the Çırpıcı Creek valley. It was located north of the Kampos (Constantinople’s version of Rome’s Campus Martius) and the Hebdomon (“Seventh [Mile],” modern Bakırköy), a coastal suburb of Constantinople located on the Via Egnatia. The reservoir supplied water to the troops and animals that mustered before and after campaigns at the Kampos. It also might have supplied water to the nearby imperial palace at the Hebdomon. It has been dated after the sixth century on the basis of the size of its bricks and the absence of brickstamps. Its Turkish name Fildamı (“Elephant Stables”) derives from a tradition that elephants from a nearby Ottoman palace were kept here. Like other surviving Byzantine open cisterns of modern Istanbul, it also functioned as a “sunken” vegetable garden (Turkish çukurbostan) by the Ottoman era. When it was documented in the late nineteenth century, shepherds reported sometimes kept their flocks in the fields. In 1968, the soil partially covering the east wall was removed, allowing for it to be better studied. It is now a park with a running track and a stage for concerts.

Also see, Cistern of Aspar, Cistern of Aetios and Cistern of Mocius

Architecture

The open reservoir of Fildamı is located on the west side of a valley running northwards from the Sea of Marmara. It is significantly smaller than the open cisterns within the city walls. It measures 127x76 m internally and its walls are visible to a height of about 10 m. It has a capacity of perhaps as much as 100 million liters (30 million gallons) of water. However, it has also been argued that it would have had a lower capacity, since water pressure would not allow it to be completely filled. The reservoir was built using an alternation of bands of brick and bands of mortared rubble faced with small stone blocks. It has five courses of brick and between two and five courses of stone. The small size of the bricks in this reservoir (around 330 mm²) suggests a post-Justinianic date, while the absence of brickstamps have been used to date after the end of the sixth century.

While its west wall is buried within the side of the valley, its east wall is free-standing. The west wall, which is around 7 m at its thickest points, has a series of 19 niches directed inward that buttressed the wall internally against the weight of the hillside. There are 21 external niches of the east wall that acted as buttresses to retain the internal water pressure. The north and south walls are narrower, measuring around 4.10 m. While they lack buttresses, each side has a double staircase on the interior. The reservoir also has convex internal corners, which strengthened the structure from the internal water pressure. Since the other open reservoirs were completely underground, they did not require similar structural reinforcement. However, the large covered Unkapanı Cistern built in Constantinople near the Pantokrator Monastery was similarly designed, with a series of niches along its two long walls.

It is unclear how the Fildamı was supplied. Since it was situated at a relatively low elevation, a number of springs further up the valley could have provided the reservoir with water. A channel from the long-distance supply line of the Valens Aqueduct or another supply line could have supplied it as well. The reservoir likely supplied water to the military camp of the Kampos and perhaps the imperial palace at the Hebdomon as well. A channel was reported leading south of the reservoir.

Unlike the open cisterns inside the city walls, this reservoir has several surviving water outlets. As the water pressure would be too great to have a single outlet for such reservoirs, several outlets were needed at different levels. There are two surviving outlets along the staircases on the south wall, the eastern one was around 1.5 m above the ground level, and the westerly one was at 4.35 m. The outlet of the north wall was at a similar level as the higher one on the south wall. All of these arched openings were recessed to house a sluice gate that managed the flow of water. The staircases on the north and south walls were supported by an arcade of five blind arches of differing heights and were built against the main walls. It is clear they were part of the original structure, but their purpose is unclear. They could have served to give access to sluice gates set at various heights in the north and south walls of the reservoir, though there are only three surviving outlets in total.

A cylindrical tower was built in the curve of a niche at the southern end of the east wall of the cistern. It is clearly a later addition to the structure since it is not bonded to the reservoir and has different masonry. It was built only with coursed rubble stonework and lacks bands of bricks except at its base. The tower consisted of concentric chambers with a central shaft enclosed by an internal spiral staircase. The channel from the main reservoir led into the outer chamber of the staircase. There were two small arched openings at a high level in the wall of the central shaft leading into the inner chamber. It seems there were openings at regular intervals allowing the water, which would have been at the same level as the surface of the reservoir, to spill over into the central shaft and exit it under a lower pressure along outflow channels leading away from the reservoir in different directions. Its design clearly indicates that it was a pressure tower intended to allow for the distribution of water from the reservoir at a reduced pressure.