The MNAC is set at the foot of Monjuic hill, overlooking the city.
The National museum Palace (as well the majority of the entire area around) was built for Barcelona 1929 World Expo.
The museum palace edifice is huge, built in neo classical style, standing on top of the path and stairway leading down from Placa de Espana, dominating the entire area.
The museum is full of art of all kinds from Romanesque era onwards, with a strong impact of religious art.
Although the entry fee is very reasonable (12 Euros) compared to other Barcelona attractions, you can visit for free every Saturday afternoon after 3 PM (be prepared for some waiting in line).
After the visit, DO have a drink (again with reasonable prices) in an outside cafe at the patio in front of the palace with outstanding views of Barcelona.