The Prado Museum is one of the finest museums in Europe. It is situated on the stylish Paseo del Prado, a lovely part of Madrid with the Retiro park just a short walk away and right next to the Ritz Hotel, the Palace Hotel, the fountain of Neptune and the stock exchange. It has some great art from artists like Goya, El Greco, Velázquez and Hieronymous Bosch. As it is a such a large museum, and can take an age to get around, you may want to consider making 2 trips to the museum (Sunday is Free!).
Tickets are priced quite cheaply 3.01 Euros / 1.5 € (Consessions) and it’s actually free on Sundays. If you’d like to do the ‘art triangle’ of the Prado, Thyssen and Reina Sofía, then you can buy an art pass for 7.66 €