The older eolianite ridges (Older Bermuda) are more rounded and subdued compared to the outer coastline (Younger Bermuda). Thus, post deposition morphology includes chemical erosion, with inshore water bodies demonstrating much of Bermuda is partially drowned Pleistocene karst. The Walsingham Formation is a clear example, constituting the cave district around Castle Harbour. The Upper Town Hill Formation forms the core of the Main Island, and prominent hills such as Town Hill, Knapton Hill, and St. David's Lighthouse, while the highest hills, Gibbs Hill Lighthouse, are due to the Southampton Formation.