The Museo Thyssen-Bornemisza is a must-visit museum in Barrio de las Letras. It houses an extensive collection of European art, spanning from the Middle Ages to the 20th century. The museum offers free admission on Mondays from 12:00 PM to 4:00 PM, allowing visitors to admire masterpieces by artists like Van Gogh, Monet, and Rembrandt. With its diverse collection and stunning architecture, the Museo Thyssen-Bornemisza is a cultural gem in the heart of Madrid.