London is the location of a castle.
London . London contains four World Heritage Sites : the Tower of London ; Kew Gardens ; the site comprising the Palace of Westminster , Westminster Abbey , and St Margaret 's Church ; and the historic settlement of Greenwich ( in which the Royal Observatory , Greenwich marks the Prime Meridian , 0 ° longitude , and GMT ) . The Tower of London , officially Her Majesty 's Royal Palace and Fortress of the Tower of London , is a historic castle located on the north bank of the River Thames in central London . In the late 15th century , the castle was the prison of the Princes in the Tower .