The interior includes a staircase of 129 steps, surmounted by a barrel vault, which gives access to the terraces and the first tier of the minaret. The courtyard façade (or south façade) of the tower is pierced with windows that provide light and ventilation, while the other three façades—facing north, east and west—are pierced with small openings in the form of arrowslits. The minaret, in its present aspect, dates largely from the early ninth century, about 836 AD. It is the oldest minaret in the Muslim world, and it is also the world's oldest minaret still standing.