Next to the palace lies a very early Islamic cemetery. A number of its inscribed tombstones date back to the Umayyad and Abbasid periods, and are currently on display at the Madaba Archaeological Museum. The palace is 70x70m in size with a circular tower flanking each corner. Three semi-circular interval towers are located along all the walls, except for the eastern side which has the entrance and two towers only. The palace was built of ashlar-cut limestone, with fresco plaster covered walls from the inside. Mosaics also covered the walls and the floors of the palace. The palace courtyard (40x40m) makes the centre of the complex, with six residential units organized around it and surrounded by a portico . Each unit comprises four rooms organized around a rectangular courtyard. Another six units were built on the second floor and are accessible by twin staircases. A water harvest system was put in place, channelling water from the roof down to cisterns using ceramic pipes. There are around 70 cisterns around the palace. The palace also has three large reservoirs (10,000 m2 in total).
There is a mosque in the complex with a minaret believed to be so far the oldest purposely built minaret in the world. The mosque’s mihrab was originally rectangular and later converted to the typical semi-circular shape. Like Qasr al-Hallabat, al-Qastal has a bath complex nearby, which was richly decorated with frescos, mosaics, marble tiled floors and carvings that depicted geometric, floral and animal motifs. The plan of the bath complex is similar to Qusayr Amra.
