While the Portunus temple is a little smaller than the other temples in the Forum Boarium and the nearby Forum Holitorium, it falls within the overall type of Late Republican temple architecture. The Temple of Portunus has a contemporaneous counterpart in the Temple of the Sibyl at Tibur (today Tivoli), which dates from around 150–125 B.C.E. Both temples were probably built by order of the Sibylline Books themselves; since they were dedicated to very different deities, this indicates that both Portunus and the Sibyl had equal status. The origins of the cult of Portunus are obscure. Some scholars believe he was a Greek god, while others think he was a Roman one. What is certain is that he was already popular when the temple was built: several Sibylline Books have been found buried in his sanctuary, which confirms its importance during his era. The Temple of Portunus is located between the two theaters in the Forum Boarium. It is one of the few temples in Rome that still preserves some of its original features, such as the entrance facade, the cella and the pronaos. Inside, there are also some traces of paintings on the walls of the temple's atrium. The current appearance of the temple is likely due to renovations or additions made in the 4th century C.E.: there are no original elements dating back to the time of Portunus.