He spent £58,000 on his royal castles, carrying out major works at the Tower of London, Lincoln and Dover. Both the military defences and the internal accommodation of these castles were significantly improved. A huge overhaul of Windsor Castle produced a lavish palace complex, whose style and detail inspired many subsequent designs in England and Wales. The Tower of London was extended to form a concentric fortress with extensive living quarters, although Henry primarily used the castle as a secure retreat in the event of war or civil strife. He also kept a menagerie at the Tower, a tradition begun by his father, and his exotic specimens included an elephant, a leopard and a camel.