Inside Achaemenid palaces, walls were mud-brick and floors were made of red-polished lime or paved with bricks or stone. There seem to have been windows at a low level and maybe also a high level, but with the large number of columns the rooms may have seemed quite dark. Despite this, the interiors were lavishly decorated, and none more so than those at Persepolis.

Huge wooden doors at palace entrances were sometimes decorated with bronze or precious metal strips showing mythical beasts. The Apadana was famed for its gigantic doors, 18 metres high and adorned with gold and silver. The doors themselves were fixed to huge poles that turned on large sunken pivot-stones above which were stone slabs decorated with floral designs.

On the inside, palace entrances were often guarded by life-sized statues of animals including seated dogs. Walls were decorated with friezes, tiles and glazed brick panels; at Persepolis examples of these have been found with floral, geometric and other designs. There would have been patterned textiles on the walls and carpets on the floors. The palaces contained huge quantities of valuable ornaments, decorations and luxurious furniture. The Greek historian Diodorus mentions that the vaults were packed full of gold and silver.

Most of these treasures were taken or destroyed by the Macedonians under Alexander in 330 BC, but some objects survived the destruction. Small statues have been found - notably a lapis lazuli head of a young Persian prince from the Apadana - and these probably stood inside false window frames or on pedestals. Remnants of burnt textiles and fragments of thin gold leaf used for gilding furniture have also been recovered.

The best finds, however, come from the Treasury at Persepolis: gold and ivory objects and gems, as well as jewellery and fragments of pottery, clay and stone. The Treasury Tablets record payments to the artisans who worked at Persepolis. These objects suggest that the Treasury may have functioned partly as a museum or a royal archive.