The Shard, London - spring saver offer - student £10.95, adult £15.95, child £9.95 when booking selected times in advance save £10 (£15 on on the day prices) - western Europe's tallest building
Also 7.07% TCB. The Shard rarely seems to do offers, spotted this and think it's excellent. You can only book for 10am, 1:30pm or 9pm on mon-fri or 10am on Saturdays. You can be up to half an hour late. Once up you can spend as long as you like , audio guides and human guides are available to ask questions to and two different levels of view, one inside and one open air.