it had once been a mosque, […] one of the biggest ever built
The short description that Byron gives of the building is quite confusing though: ‘the Ark, or Citadel, a mountain of small russet bricks laid with a consummate art, which looks as if it had once been a mosque, and if so, one of the biggest ever built’. From this short description it is not clear what was the original purpose of the building: was it a mosque or a citadel? Actually, it was both, but in the mind of its patron, it was a mosque.
The patron was Ali Shah, wazir during the reigns of Uljaytu, the same ruler of the Dome of Sultaniyya, and of Abu Sa’id. According to the sources, Ali Shah was not only the patron of the immense building but also its designer. The building is named after him: Masjid-i Ali Shah, or Arg-i Ali Shah.
In the mind of its designer and patron, the mosque needed to be a huge, massive construction. The plan developed around an enormous courtyard, paved with marble, 286 meters long and 229 meters wide. In the center of the courtyard, an elevated square platform contained an octagonal fountain with four lions sprouting water from their mouths in every direction. Trees were neatly organized in each of the four corners surrounding the platform with the fountain.
The entrance, a pishtaq, was at the center of the northern wall. The mosque had two iwans at the center of the East and West walls, and a larger iwan was on the Southern part. Also in the case of the big iwan, the dimension were huge, the vault being 30.5 meters wide and 48 meters deep with a total distance between the portal and the mihrab of 65.5 meters. This massive construction was made entirely of bricks.
Perhaps because of the size of the building and particularly of its massive walls, the mosque was later used as a citadel, thence the name ‘Arg’.
The hugeness of the monument also determined its collapse: not a lot remains today of the once biggest mosque ever built.
Further information and images can be found on archnet.org