My personal favourite is the Natural History Museum.
What it contains is interesting enough, but it's the Waterhouse building itself that never fails to take my breath away.
The terracotta facade, with its sculptures of extinct and extant beasts and birds, is worth spending a half-hour or so admiring outside, before going in to see the grandeur of the great hall. Alfred Waterhouse, the architect, said of this building:
"...wherever I thought that the particular objects in view could not be best obtained by a strict obedience to precedent, I took the liberty of departing from it."The new Darwin centre sits a little uneasily beside his masterpiece, as does the Earth Gallery before it, though it was always intended that the west and east wings would be built, but sadly, budgetary considerations put paid to that.
It's a true masterpiece of Victorian design, and no modern building in London can hold a candle to it.
Tomorrow - C is for Comic.