See also:
1. Museo de Reina Sofia
The Reina Sofia is Madrid's world-famous modern art gallery - and it has free entry for a limited time every day. That means you can see many works by Salvador Dali and Pablo Picasso - including the latter's masterpiece, the Guernica - completely free.When is it free? Monday, Wednesday, Thursday and Friday from 7pm until 9pm. Saturday afternoons (from 2.30pm) and Sunday mornings (until 2.30pm). At other times it costs 6€€ to get in. The museum is closed on Tuesdays.
2. Museo del Prado
Officially Spain's most popular tourist sight and free six days a week! The Museo del Prado is Spain's premier art gallery, housing the finest works of art Spain has ever produced.
When is it free? 6pm until 8pm from Tuesday to Saturday and 5pm until 8pm on Sundays.
More: Madrid's Best Museums
3. Palacio Real (Madrid's Royal Palace)
The royal residence, just five minutes walk from Plaza Mayor.
When is it free? Wednesdays.
4. Museo Tiflológico
The Museo Tiflológico is Madrid's Blind Museum, maintained by ONCE, the Spanish blind association. Not so much about the blind as for them - which means lots of touchy-feely exhibits that anyone can enjoy. A bit different from the average museum.
When is it free? Always!
More: Museo Tiflológico
5. Anden 0
The old Chamberi metro station was closed for many years, gathering dust (one hell of a lot of dust) under the streets of Madrid. But now it has reopened about a museum showing the history of Madrid's metro system. One for train fans and anyone interested in a quirky side to Madrid's history.
When is it free? Every day (apart from Mondays, when it's closed).
More: Anden 0
6. Espacio Conde Duque
Former barracks that now houses a number of interesting sights. The main attraction is the contemporary art museum, but there is also the Conde Duque, the city archive, libraries of history, music and newspapers and the artisan printing press.7. Madrid's Museo Taurino (Bullfighting Museum)
If you can't get to see a live bullfight in Spain, at least check out the bullfighting museum, which explains the history of the Spanish pastime and features some pretty gory artifacts - including bulls' heads and blood stained costumes from matadors that have died fighting.
When is it free? Always.
More: Museo Taurino in Madrid
Read more about Bullfighting in Spain.
8. Go for a 'Paseo' Through Madrid's Historic District
Walking's free! Madrid doesn't have a great deal of picturesque areas, but a 90 minute walk from Puerta del Sol to Plaza Mayor and then on to the Plaza Oriente (where the Royal Palace can be found), coming back on yourself along Gran Via, before walking along the Paseo del Prado and finishing at Atocha.
When is it free? There's never been a tax on walking.
9. Museo Archeológico Nacional
An above-average archaeological museum, with its main attraction being a replica of a prehistoric cave.
When is it free? Saturday afternoons and all day Sunday.
10. El Parque del Buen Retiro
The Retiro is Madrid's grand park, slap-bang in the middle of the city. With a lake, trees, flower gardens, chapel ruins and the Palacio de Cristal, it makes a perfect (and close) retreat from the hustle of Madrid's city life.
When is it free? Always!
