In London, it's all about the history, the only tall buildings you'll see is where all the banks are. Since London was probably second only to NY or Paris in Banking.
We have the royals, Buckingham palace, the South banks and the Thames, the London Eye along with it, Big Ben in that vicinity too. Many old and new Galleries and Museums. Hyde Park.
Best part about London I feel is the accessibility. Underground trains with small stations literally less than km in either direction from the other. Where the tube can't take you, the buses do. If you want to travel out of London, then there's overground stations.
The cabs here are good too, but expensive.