Tower of London
Greater London, England
Tower of London is a castle in Greater London, England, first built in the 11th century. It is a World Heritage Site. The nearest other castle is Baynard's Castle, 1.1 mi away. It is owned by Charles III.

Tower of London at a glance
Built
1066
11th century
Type
Castle
Cared for by
Charles III
Heritage status
World Heritage Site
scheduled monument
About Tower of London
The Tower of London, officially His Majesty's Royal Palace and Fortress of the Tower of London, is a historic citadel and castle on the north bank of the River Thames in London, England. It lies within the London Borough of Tower Hamlets, which is separated from the eastern edge of the square mile of the City of London by the open space known as Tower Hill.
From the Wikipedia article on Tower of London, CC BY-SA 4.0.
Tower of London sits at 51.5082, -0.0762 in Greater London. The closest other castles are Baynard's Castle (1.1 mi), Montfichet's Tower (1.1 mi) and Greenwich Castle (3.8 mi).