FIDENAe, identified with the modern Castello Giu-bileo, an old and important Latin city on the left bank of the Tiber, about five miles above Rome. It is said by Livy to have owed its origin to the Etruscans; but his testimony is not supported by any other historian. There i≡ no Latin city which plays so important a part in the annals of regal Rome. According to the tradition of the Roman historians, hostilities first broke out between the two cities in the time of Romulus, and continued with little intermission and various success till 496 b.c., when, being abandoned by its allies, it was forced to yield to the Roman arms. In 438 b.c. the Fidenates revolted and slew the Roman ambassadors, but after maintaining for twelve years an unequal contest, their city was taken and plundered, and themselves sold into slavery. From this time Fidenae almost disappears. In the later period of the republic, and under the empire, it was a small country village, and it is mentioned by Horace as almost proverbially desolate. In the reign of Tiberius it acquired a dismal notoriety: an extraordinary gladiatorial show had attracted vast multitudes from Rome and the surrounding country, and the wooden amphitheatre in which they were accommodated fell during the exhibition, and destroyed, it is said, nearly 50,000 persons. No ruins of Fidenae now exist.