Behind Ark citadel there is a building of medieval amir prison - 'zindan'. This high construction looks like a small fortress and today it is a museum. In the past this prison consisted of two parts. In the first part prisoners were put in cells situated in several yards. A deep hole was a place for criminals in the second part. They were lowered there with special ropes so was their food. The word 'zindan', in Persian means 'underground, darkness'. Twice a month prisoners were taken from the dungeon to Registan where amir decided who was to be killed and who to pardon.