Construction of Topkapi Palace started in the middle of the 15th century, a few years after Ottomans conquered Constantinople, nowadays Istanbul. Its name means Cannon Gate, and it served as the main residence of Ottoman sultans, and also as an administrative headquarters. The complex was expended and had major renovations from earthquake and fire damages. Topkapi serves as a large museum since 1924. Visitors can have a glimpse into sultans lifestyle. Not all parts of the luxurious complex are available for visitors. Among others, tourists can visit Imperial Harem and Imperial Treasury.