The Starry Sept is a large sept near the Honeywine in Oldtown. It was the seat of the High Septon for at least a thousand years prior to the War of Conquest. The Starry Sept has black marble walls and arched windows.
When Aegon I Targaryen landed at the mouth of the Blackwater Rush, the High Septon in Oldtown locked himself inside the Starry Sept and prayed for seven whole days while refusing to eat or drink. At the end of the seventh day he emerged from his fast and declared that the Faith of the Seven would not fight Aegon's Conquest, proclaiming that if they did Oldtown would burn and the Starry Sept would be destroyed. Lord Manfred Hightower heeded the prophecy and welcomed Aegon when he appeared before his gates. Aegon was then annointed in the Faith when he became Lord of the Seven Kingdoms.