A 13th-century almshouse chapel attached to the old garrison hospital, used as a chapel by the Portsmouth military garrison for centuries. The medieval chancel and a few of the original windows still stand. The Georgian and Victorian nave was destroyed by German firebombing in 1941 and never rebuilt — the open shell, with the chancel roofed and the nave open to the sky, is now maintained by English Heritage.
It sits on the Hot Walls overlooking the harbour mouth. Open occasionally on summer afternoons; the rest of the time you can walk around the outside and read the boards explaining its history. Free.