Temple of DebodTemple of Debod is an Egyptian temple donated to the country of Spain by the Egyptian government. It dates back to the 2nd century BC and was built to praise the Egyptian god Amun and the Egyptian goddess Isis. Unfortunately, the temple is currently not open for the general public, but you can still visit its walkway and closely explore its exterior.
Church of San Antonio de los AlemanesThis is a 17th-century baroque church, which has a breathtaking interior, entirely painted by fresco. Entering the church costs the symbolic price of 2 euro, and visitors are always welcome to enroll a guided tour through its secrets.
Catedral de Sta Maria la Real de la AlmudenaThis is a Cathedral built in the Neo-Gothic style. The temple is particularly famous for the 16th-century image of Virgen de la Almudena -the patroness of the city - which is housed inside the crypt. The admission to the cathedral is free, but you will probably be asked to make a symbolic 1 euro donation for the building's maintenance. If you care to see more, you can also visit the Museum of the cathedral. (Additional category - Museums & Galleries)
San Jeronimo el RealThis is the traditional Gothic church where Spanish kings and queens were crowned from the 16th century up until this very day. This is also where the Spanish royalties are buried in their crypts. The entrance to the building is free, and you'll be lucky to witness some of the church concerts, held every now and then.
Basilica de San MiguelThis is one of the most prominent examples of Spanish baroque, located in Hapsburg Madrid. Though not great in size, the basilica has a unique design, which makes it stand out in a way. The admission to the building is free, yet you should check opening hours beforehand.