In 1245, seven years before becoming the King of Castile and León, Prince Alfonso defeated the Moors and claimed Cartagena. He then declared the city to be a Christian Diocese. This prompted the construction of Cartagena Cathedral. It was rebuilt and expanded in the 16th century, late 17th century and early 20th century. During the Spanish Civil War (1936 – 1939), the Cathedral of Santa María la Vieja was destroyed. It remains in ruins. The building’s shell is adjacent to the Roman Theatre. This positioning is a coincidence because the former amphitheater was buried and unknown when the cathedral was first constructed during the 13th century.