On the right hand side of the transept is the Royal Pantheon a room built in the end of the 18th century in neo-gothic style, it is the earliest neo-gothic building in Portugal to house to tombs of the Portuguese monarchy.
The Royal Pantheon has the 13th-century tombs of the Queens of Portugal, Urraca of Castile and Beatriz of Castile, married respectively to Kings Afonso II and Afonso III. Besides, there are smaller tombs of unidentified princes. The most remarkable tomb is that of Queen Urraca (died in 1220), buried in a richly decorated late romanesque tomb. A relief showing the Queen is seen over the tomb, and the sides are decorated with the Apostles under round arched gallery. Other reliefs show the King, surrounded by their children, mourning the late Queen, as well as Christ surrounded by a mandorla and the symbols of the Four Evangelists. Other tombs are richly decorated in the arabesques of mudéjar-romanesque style and with images of the Apostles.