Temple of Jupiter, Split, Roman temple in Diocletian's Palace, Split, Croatia

The Temple of Jupiter stands in the western religious part of Diocletian's Palace, near the Peristyle. Its barrel coffered vault and richly decorated doorways survive, while reliefs of Victoria, Triton, Helios, Hercules, Jupiter and Apollo are set above the entrance. A black granite sphinx from Egypt stands before the facade, and the high podium conceals a crypt once dedicated to St. Thomas.

Built between 295 and 305 as part of Diocletian's Palace, the temple was dedicated to Jupiter, the emperor's "divine father". Work stopped when Diocletian abdicated in 305, leaving parts unfinished. By the 6th century it had become the baptistery of St John the Baptist, with a crypt dedicated to St Thomas. A Romanesque bell tower added in the 11th century was removed around 1840.

The temple's entrance is guarded by a sphinx of black granite, placed there in 1928, one of twelve Diocletian brought from Egypt. Inside, the 13th-century baptismal font was assembled from marble panels of an 11th-century altar screen from the cathedral; one panel carries the earliest stone depiction of a Croatian king, Krešimir IV or Zvonimir. A bronze statue of St. John the Baptist by Ivan Meštrović stands within.

The temple stands at Kraj sv. Ivana 1, in the western, religious part of Diocletian's Palace, a short walk from the Peristyle. The entrance is reached on foot through the palace streets; the crypt of St Thomas lies beneath the high podium, and the northwest corner still has a house leaning against it.

The black granite sphinx in front of the temple was set there in 1928, not in antiquity; it is one of twelve Diocletian brought from Egypt. The 13th-century baptismal font is built from marble panels of an 11th-century altar screen from the cathedral, one carved with the earliest stone portrait of a Croatian king.