The fortress is the reason most people come to Hisar. It sat on a low hill commanding the approach from Dushanbe and served as the regional headquarters of the Bukharan emirate until the early 20th century. The walls, gates and towers were repeatedly destroyed and rebuilt — the current main gate, a tall arch in honey-coloured brick, is a 1980s reconstruction of an 18th-century original.
Walk up through the brick gateway and the hilltop opens onto a wide, mostly empty plateau with low remains of foundations and a few cannons. The views back over the Hisar valley and toward the snow-capped Hisar Range are the best part of the visit. Entrance to the wider complex is free; a small fee covers the museum and the madrasas at the base of the hill.