In the 2006 Christmas Special The Runaway Bride, during which fans met Donna Noble for the first time, the Empress of Racnoss (basically a giant spider from outer space) built her nest underneath the Thames Barrier. In retrospect, setting up base underneath tonnes of water probably wasn't the best idea she ever had, was it? It did give us one of the most epic episode conclusion to date, though, so fans can thank her for that at least. Nearest Tube: Pontoon Dock DLR