Queen Sofia Arts Center

The Centro de Arte Reina Sofía is Madrid's modern art gallery, and along with the Prado and the Thyssen-Bornemisza, makes up the city's threesome of great museums. About 1,000 works are spread across four floors, but probably the most famous work is found on the second floor. Picasso's Guernica is the museum's crowning jewel.

As is the case with other modern art museums, travelers say you'll especially enjoy Queen Sofia if you appreciate modern art. If you're not a huge fan, you might want to spend your time at the Prado or Thyssen-Bornemisza. Note that you can skip out on the admission price by visiting the museum during its free hours -- Saturday after 2:30 p.m. or all day on Sunday.