The Porto Cathedral (Sé do Porto in Portuguese) is the most important religious edifice in the city and has been declared a National Monument. It is situated in the upper part of Porto. The Cathedral is in Batalha, very close to the walls that once protected the city. The building looks a bit like a fortress with crenels from the outside. The construction of the Cathedral began during the twelfth century, but it was rebuilt and renovated numerous times throughout the centuries. This explains why the Cathedral is a mix of architectural styles. The temple is predominantly Baroque in style, although its façade and the nave are Romanesque and its cloister and one of the chapels are Gothic in style. Inside, the large pillars make the nave seem narrow with a high ceiling. It has a restrained decoration with bare walls, and only the high altar and some of its chapels are decorated in a Baroque style.