Noushabad Castle

Iran, Iran

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Noushabad Castle, more accurately called Sizan Castle (sometimes also spelled Sīzān or Kheshti Castle), is a large medieval mud‑brick fortification in the town of Nushabad (also written Noushabad, Nush‑abad) in Aran and Bidgol County, Isfahan Province, Iran.

The castle dates to the Seljuk period (roughly the 11th–12th centuries CE) and is described as one of the most magnificent solid mud castles in Iran, built with thick mud‑brick walls and surrounded by nine round towers. It sits above and around the famous Ouyi underground city, a multi‑level subterranean refuge dug 4–18 meters deep under Nushabad, which was originally created in the Sassanid era (about 1,500 years ago) and later used through the Seljuk, Safavid, and even Qajar periods as a hidden shelter against invasions and attacks.

The underground city is a complex network of tunnels, chambers, vertical shafts for air and light, and hidden entrances in houses, mosques, qanats, and the castle itself, allowing residents to retreat unnoticed and live for long periods with their own living spaces, storage, water, and even toilets. Sizan Castle functions both as a historic fortress and as a landmark that marks the entrance area to this underground world.