Castle

Castles were large fortified buildings, often used as the residence of royalty or nobility. On Earth, castles were usually located in Europe.

Castles on Earth
Castles located in Great Britain included Windsor Castle in England (DW: Silver Nemesis), Balmoral Castle in Scotland (DW: Tooth and Claw), and Cardiff Castle in Wales (TW: Everything Changes). A castle in Wessex was taken over by Irongron while the nobleman who owned it was away, but it was destroyed when Linx's spaceship exploded. (DW: The Time Warrior) A castle owned by Lord Geoffrey de Beauvain was taken over by Lord Waldean de Beauvain. (TVC: The Magician)

Other Earth castles included Drachensberg (NA: Timewyrm: Exodus) and Colditz Castle (BFA: Colditz), both in Germany.

Some castles were converted into other uses. One became Stangmoor Prison (DW: The Mind of Evil), while another was used as the Pharos Institute's headquarters (SJA: The Lost Boy) One castle in Scotland was used by the Quarks as their base, but it was destroyed by the Second Doctor and Jamie McCrimmon. (TVC: Invasion of the Quarks)

Castles on other planets
On Tara, Castle Gracht was the residence of Count Grendel of Gracht. (DW: The Androids of Tara) On an unnamed planet, the spacecraft Hydrax was converted into a castle by the Three Who Rule. (DW: State of Decay) Castle Extremis was used to host the signing of the peace treaty between the Anthium and the Zerugma. (NSA: Martha in the Mirror) The residents of one unnamed planet, who were threatened by Mirrorlings, put all their mirrors in a castle to protect themselves. (DWA: Mirror Image) Zentor lived in a castle on the Haunted Planet. (TVC: The Haunted Planet)

According to an apocryphal account, the Master attempted to capture the Doctor in a castle on Tersurus. (DW: The Curse of Fatal Death)

Castles in other dimensions
The Gateway was a castle used by the Tharils as the centre of their empire. (DW: Warriors' Gate) Morgaine lived in a castle in her home dimension. (DW: Battlefield) The Pied Piper lived in a castle when he took the children of Hamelin to his own realm. (TVC: Challenge of the Piper) Eugene Tacitus' prison took the form of a medieval castle. (BFA: The Holy Terror)