In message , John Rowland
writes
Chiswick...
http://maps.google.co.uk/maps?hl=en&...1364&panoid=xd
h7tS2mgnvBYYObY_AaBw&cbp=12,163.5,,1,10.46
The ground inside the dome is noticeably curved downward.
That's to help the water drain away - it's the remains of an ice house.
--
Paul Terry