If you only have time for one cultural visit, make it the British Museum. Its amazing. The museum's exhibitions are divided by civilizations, with wonderful displays informing the visitorof those of Greece, Rome, Egypt (the collection of Mummies is exceptional) and the Oriental East. Artefacts include such revered items as the Elgin Marbles (involved in an ongoing cultural tug-of-war between the British and Greek Governments) and the Rosetta Stone (the key to translating hieroglyphics). In fact, there are artefacts from all over the world that have been donated by collectors, and some say those artefacts should be returned – but what a chance for the visitor to see all this richness together.  You’ll need a long time to see even a small amount, so plan for at least half a day (and it isn’t really for long treks by small children, though you could do a hit and run because it is free). Have a look at the good stuff on the museum website: www.thebritishmuseum.ac.uk