The oldest part of the Ösmo Church was constructed in the latter part of the 12th century. The church was modernized in the 14th century, when the old chancel was demolished and replaced by one which was both taller and wider. The church largely gained its present appearance during the 15th century.
The interior of the church is decorated with frescoes added just after the middle of the 15th century. It is said that they were painted by Albertus Pictor, the most famous church artists of the medieval period. The church also contains a large number of coats of arms used in processions, and a triumphal crucifix.
References:The Cathedral of Saint Mary Major, often called Lisbon Cathedral or simply the Sé, is a Roman Catholic cathedral located in Lisbon, Portugal. The oldest church in the city, it is the seat of the Patriarchate of Lisbon. The cathedral has survived many earthquakes and has been modified, renovated and restored several times. It is nowadays a mix of different architectural styles.
The site where it stands was the principal mosque of Lisbon when it was an Arab settlement. The construction of the cathedral started around 1150, three years after the city was conquered from the Moors during the Second Crusade. Shortly after the victory the English knight Gilbert of Hastings was named bishop of the city of Lisbon.
One good reason to visit the Cathedral is to visit its charming cloisters located in the back. There are several tombs in the cathedral, the most notable of which is the beautifully sculpted tomb of Lopo Fernandes Pacheco and his wife.