4sided stone pillar with pyramid on top and relief carving on all four sides

It is an obelisk. The first obelisks were built by ancient Egyptians, at the entrance of their temples. They probably symbolized Ra, the god of the sun. At roughly the same time, Assyrians built them as well, to celebrate the achievements of their kings. Then, the ancient Greeks adopted this type of building, and after them the Romans, as well as the Turks in the Middle Ages.