The Louvre is the world's largest art museum and an historic monument. Originally built as a fortress in the late 12th century, it was transformed into a royal palace before becoming a public museum in 1793. The Louvre houses an extensive collection of art and artifacts, spanning over 9,000 years and including masterpieces from various civilizations. Notable works include Leonardo da Vinci's Mona Lisa, the Greek statue Venus de Milo, and the ancient Egyptian sculpture Great Sphinx of Tanis. The museum's iconic glass pyramid entrance, designed by architect I. M. Pei, is a modern addition completed in 1989, blending contemporary design with the historic architecture of the palace. The Louvre attracts millions of visitors annually, making it one of the most visited museums in the world.