It was built during the construction of the whole palace. At the entrance to the temple there is a sphinx from Egypt brougt to Split ​​by order of emperor Diocletian. Temple of Jupiter was constructed from the 295. to 305. as part of the palace of emperor Diocletian.
It was probably dedicated to the supreme deity of the Romans, Diocletian's divine father Jupiter. The temple is located west of the central part of the palace which was the religious part. During Late Antiquity and Middle Ages, the temple was converted into a baptistery and the crypt was dedicated to St. Thomas. Inside the temple there are two preserved sarcophagus in which archbishops of Split, Ivan and Lovro, are buried. Exceptional Mestrovic's statue of St John the Baptist is also located in the interior.