Westminster Cathedral
Worth a quick visit if you are passing. The brick and stone neo-Byzantine Catholic Cathedral (not to be confused with the much more famous Westminster Abbey) is near Victoria Station, just off Victoria Street. Construction started in 1895, and some of the interior is still unfini

Worth a quick visit if you are passing. The brick and stone neo-Byzantine Catholic Cathedral (not to be confused with the much more famous Westminster Abbey) is near Victoria Station, just off Victoria Street. Construction started in 1895, and some of the interior is still unfini
Check the official site before travelling; hours and prices can change.
More museums

Sir John Soane's Museum
Free, tiny, deranged — Soane's own house preserved exactly as he left it in 1837.

The Wallace Collection
Free national museum in a Manchester Square townhouse — armour, Boucher, the Laughing Cavalier.

The British Museum
Free, vast, civilisationally heavy — go for one room, not all of them.
Source: wikivoyage