Just discovered that there are 10 castles or sites thereof the former in Dundee City.
Castles inside Dundee City limits:
Invergowrie Castle (Dickson Avenue, demolished)
Dundee Law (Iron age hill fort)
Jedburgh Castle (fortified house, Blackness Road)
Dudhope Castle
Dundee Castle (Castle St, demolished)
Mains Castle, Caird Park
Claypotts Castle (Arbroath Road)
Broughty Ferry Castle
Powrie Castle (New)
Powrie Castle (Old)
That must be some sort of record for castle density for a city.