It is decorated with corals and has a built-in holster for a trident. It is described as a deep-sea fishing chair.
The throne is placed on the right side, the males' side of the Hall. It is the first in the line because he is one of the Big Three and one of the eldest gods. His throne is before Hephaestus' Throne and is opposite to Demeter's Throne.
Poseidon's throne was made of gray/green white streaked marble. The arms were sea beasts and he sat on a seal skin. It was decorated with coral, gold chips and pearls.
Percy Jackson once sat on it trying to communicate with his father during the Battle of Manhattan on Mount Olympus, and he felt the power of sea at his disposal. It was so powerful that Percy nearly spontaneously combusted, for when he jumped down from the throne after trying to contact his father, Grover comments on the smoke coming off of Percy, and the fact that he turned pale. When Poseidon started talking to Percy, he claims he would have blasted Percy if he hadn't looked, and saw it was Percy, not an attacker (to Percy's relief). In the end, Poseidon forgave Percy for sitting on his throne, since it was an emergency. Percy describes how he felt when he sat on Poseidon's throne: like he was controlling the whole ocean. He realized how powerful his dad was and felt as though Poseidon should be the one in charge, and thought of how it must be with eleven other gods all trying to get their own way. This shows how Poseidon probably felt but controlled himself (as Percy did). When Kronos made his way up into the Hall of the Gods he tried to destroy Poseidon's Throne. Percy was able to cut Kronos' armor and drive him away.