20 Fenchurch Street, front left, nicknamed 'the Walkie-Talkie'

Sky Garden offers view over London on the 35th and 36th floors. Access is free but tickets notoriously difficult to get as they are made available on a Monday 3 weeks in advance. You can also freely visit the garden if you book a table at the Darwin Brasserie, but quite frankly over priced, food average and they charge you for tap water!!!!! (filtered, apparently.... )