On the west side of the King Alfred lies this area of grass which seems to be a forerunner of the modern 'green roof' concept. The area underneath was designed as an underground car park and the access ramps can still be seen on the seaward side of the building. In the 50's part of the underground area was devoted to table tennis. By present standards it held a derisory number of cars and there may have been safety issues. It was later converted to ten-pin bowling.
It is of course not 'waste land' but a 'waste roof'. It seems a pity it can't be put to good use but it would probably need rebuilding from the foundations up if it is to support anything more than itself, especially to modern safety standards.
See:- "King Alfred Ice Rink"