The photo shows the wonderful craftsmanship of both the iron work and stone work of Inigo Jones's Tulip Stairs. The interlocking stairs support each other and that can be seen in the puzzle-like way the stairs fit together at the egdes. The flower designs are called tulips, but I've read that they are more likely modeled after lilies.
The first self-supporting spiral staircase in England is in The Queen's House. It is part of the National Maritime Museum, #Greenwich, London, #England. #photography #Support_Public_Lands #architectural_detail