The Heygate Estate in Elephant and Castle is one of London's ugliest blocks - but the view of the city skyline from the top floor is amazing. You can see in this photo the view of the City, including St Paul's cathedral.
The building is gradually becoming derelict - flats are being vacated and boarded up, ready for the towers' (there are five of them) demolition in 2010. I think there was only one flat still being inhabited on this floor. It's eerily silent.