Fort Jay, located at the center of the original (northern) portion of Governors Island, is the oldest, having been built in 1794. It was built on the highest point of the island, with a glacis sloping down from all sides. The initial fortifications degraded to such a point that they were replaced in 1806. Fort Jay was initially named for New York governor John Jay, but after being rebuilt, was known as Fort Columbus until about 1904. The rebuilt fort, which reused the original glacis and many of the original walls, comprised "an enclosed pentagonal work, with four bastions of masonry, calculated for one hundred guns", and initially included a 230-person brick barracks. Though Fort Jay has been renovated multiple times throughout its history, its current appearance largely stems from renovations in the 1830s. The walls of Fort Jay are made of sandstone and granite, with an arrow-shaped ravelin on the northern wall. The fortification is surrounded by a moat that is now dry.