Can you tell me what are these red metalic structure around london which look like giant circus/basket/... ?

Question

I join an exemple it will be easier to understand : http://maps.google.co.uk/maps?f=q&hl=en&geocode=&q=se166sf+london&ie=UTF8&t=h&layer=cx&ll=51.502589,-0.047899&spn=0.001459,0.004828&z=18

Answer 1

Erm. Flower baskets?

Answer 2

It's a gas-holder - a large cylindrical tower used to store gas.  They've been a feature in Britain for many years.  To see how they look side-on, see the link below.