This lavish palace was the royal residence of the Ottoman empire for almost 400 years. Here, you can peek into the imperial life of the sultans as you wander through the grand courtyards, pavilions and ceremonial rooms that display an impressive collection of artefacts and treasures. With a separate ticket, you can also venture into the Harem—a private world decked with over 400 exquisitely decorated rooms where the sultan shared with his wives, concubines and children. To skip the snaking lines, buy a fast-track ticket or a multi-day Museum Pass, which provides access to the city’s other top sights. – Tripadvisor