The citadel of Bust is a fortified mound whose age is unknown but almost certainly predates the rise of Islam, as epigraphic and ceramic evidence from the surrounding area date back to the Achaeminid period (6th-4th c. BCE). A walled city adjoined the citadel to the north. In the Islamic era, the site prospered during the Ghaznavid and Ghurid periods (11th-12th/5th-6th c. AH), when the area outside the enclosure walls expanded to the north and the Ghaznavid sultans constructed a palatial city known as Lashkar-i Bazar. Evidence of rebuilding during the Timurid period suggests that the citadel itself saw renewed habitation after the Mongol sack of Bust in 1220/618 AH.

The site is located on a triangular peninsula formed by the confluence of the Helmand River and the Arghandab River. The Helmand flows roughly from north to south in this region and passes the citadel on its west side, while the Arghandab makes its course roughly from east to west, then turns toward the south to meet the Helmand, passing to the east of the citadel. The surrounding terrain is low-lying and the citadel commands an expansive view in all directions. 

The citadel proper includes a mound on its west side, rising some 20 meters high, and a terrace sloping to a lower area closed off by a wall and a moat. Islamic-period ruins atop the mound include a large rectangular enclosure with fortified towers and a seven-story sardab surrounded by galleries. Among the Islamic structures within the lower enclosure is the Arch of Bust, dating to the Ghurid period.

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