The Almudena Cathedral (Catedral de Santa María la Real de la Almudena) is the cathedral of Madrid. It was built between 1883 and 1993.
Admission to the both the cathedral and crypt is free but a suggested donation of €1 is asked in order to provide for maintenance and pay for operating costs (as of August 2023). It’s open daily from 10am to 9pm in the summer and 9am to 8:30pm the rest of the year. The main entrance for tourists is on the east side of the building while the crypt entrance is at the rear of the building.
On the side opposite the Royal Palace is the entrance for the self-guided tour of the church and museum, which also provides access to the rooftop terrace. It costs €7 per person (as of August 2023). It’s open Monday through Saturday from 10am to 2:30pm. Photos are not allowed inside the museum.