is on its east side. In the centre of the Sharhryar Ark is the Seljuk palace, probably built by Sanjar. The surviving mud brick walls lead to the conclusion that this palace, though relatively small, was composed of tall, single-storey rooms surrounding a central court along with four axial iwans at the entrance to each side. Low areas nearby seem to indicate a large garden, which included an artificial lake; similar gardens were found in other Central Asian palaces. Any remnants of interior or exterior decoration have been lost because of erosion or theft. Another notable Seljuk structure within the Shahryar Ark is the kepderihana (from the Persian, "Kaftar Khaneh", or "pigeon house", i.e., the columbarium). This mysterious building, among the best-preserved in the whole Merv oasis, comprises one long and narrow windowless room with many tiers of niches across the walls. Some sources Believe the kepter khana (there are more elsewhere in Merv and Central Asia) was a pigeon roost used to raise pigeons, to collect their dung, which was used in growing the melons for which Merv was famous. Others see the kepderihanas as libraries or treasuries, because of their location in high status areas next to important structures. The best-preserved of all the structures in Merv is the 12th-century mausoleum of Sultan Sanjar, also in Sultan Gala. It is the largest of Seljuk mausoleums and is also the first dated mosque-mausoleum complex, a form which was later to become common. It is square, per side, with two entrances on opposite sides; a large central dome supported by an octagonal system of ribs and arches covers the interior (Ettinghausen, 270). The dome's exterior was turquoise, and its height made it imposing; it was said that approaching caravans could see the mausoleum while still a day's march from the city. The mausoleum's decoration, in typical early Seljuk style, was conservative, with interior stucco work and geometric brick decoration, now mainly lost, on the outside. Except for the recently "reconstructed" exterior decoration, the largely intact mausoleum remains just as it was in the 12th century. A final set of Seljuq remains are the walls of the Soltangala. These fortifications, which largely remain, began as mud brick structures, inside of which were chambers for defenders to shoot arrows from. There were horseshoe-shaped towers every . These walls, however, did not prove to be effective because they were not of adequate thickness