Tower of London

The Tower of London is officially Her Majesty's Palace and Fortress, The Tower of London, although the last ruler to reside in it as a palace was King James I (1566-1625). The White Tower, the square building with turrets on each corner that gave it its name, is actually in the middle of a complex of several buildings along the River Thames in London, which have served as fortress, armoury, treasury, mint, palace, place of execution, public records office, observatory, refuge, and prison, particularly for upper class prisoners.

More info at  en.wikipedia.org