Bulgaria, Ostrusha ancient Thracian tomb

The Ostrusia Mound is a Thracian burial site near Shipka, Bulgaria, built in the 4th century BC. It features a large tomb complex with six rooms, professionally excavated in 1993. The chambers contain granite blocks and damaged frescoes, with some artifacts like a noblewoman's portrait and silver vessels. The temple's architecture includes a long entry corridor, an ante chamber with sacrificial remains, and a central room with a Doric column symbolizing the sun, reflecting Thracian cosmology.

Describe the central room of the tomb.

What do the tomb's columns represent in Thracian beliefs?