One of Istanbul’s most impressive sites is the Topkapi Palace, which for around 400 years served as the imperial enclave of the Ottoman sultans. Construction began in 1459 under Sultan Mehmed II and, at its peak, housed around 4,000 people. When the Ottoman Empire ended in 1923, the complex was transformed into a museum. It includes four main courtyards and many smaller buildings which house both Islamic and Christian relics including weapons, armor, manuscripts, jewellery and treasures. Its most famous pieces are perhaps Prophet Mohammed’s cloak and sword. There are impressive views over the Bosphorus from the Palace, which is now part of Istanbul’s UNESCO World Heritage Listed sites.