The Arg-é Bam was the largest adobe building in the world, located in Bam, a city in the Kermān Province of southeastern Iran. It is listed by UNESCO as part of the World Heritage Site "Bam and its Cultural Landscape". The origin of this enormous citadel on the Silk Road can be traced back to the Achaemenid period (6th to 4th centuries BC) and even beyond. The heyday of the citadel was from the 7th to 11th centuries, being at the crossroads of important trade routes and known for the production of silk and cotton garments.
The entire building was a large fortress in whose heart the citadel itself was located, but because of the impressive look of the citadel, which forms the highest point, the entire fortress is named the Bam Citadel. On December 26, 2003, the Citadel was almost completely destroyed by an earthquake, along with much of the rest of Bam and its environs. A few days after the earthquake, the Iranian President Mohammad Khatami announced that the Citadel would be rebuilt.
Larger than nearby Arg-é Rayen, the area of Bam Citadel is approximately 180,000 square meters (44 acres), and it is surrounded by gigantic walls 6–7 metres (20–23 ft) high and 1,815 metres (5,955 ft) long. The citadel features two of the "stay-awake towers" for which Bam is famed - there are as many as 67 such towers scattered across the ancient city of Bam.
When the gate of the city was closed, no human or animal could enter. The inhabitants could continue living for a long period of time in isolation as they had access to a well, gardens, and domestic animals inside. When the fortress-city was besieged the inhabitants could remain in the city while the soldiers could defend it, protected by high walls and towers.