Savannah is built on what was an island thousands of years ago. As the ocean receded, the island became what today we call a bluff. When looking for a site to establish the Colony of Georgia, James Oglethorpe chose the bluff because of the excellent defensive position it provided.
But in the early part of the 1800's, parts of the bluff began to break away and fall down toward the river below. To counter the problem, the city contracted with a prominent architect of that time to build a retaining wall. That man's name was Charles Cluskey.
However, the city was not in a position to pay Cluskey. So he offered them a deal. Instead of payment, the city would allow him to cut five vaults into the wall which he could rent out for storage.
Today, the four larger vaults , known as Cluskey's Vaults, have been restored. They are open for all to stop in and explore as you walk down the Drayton Street ramp to the river.