Located three miles from what is now the mouth of the Tiber River is the archeological site of the ancient city of Ostia, once the harbor city of ancient Rome. The ruins—including homes, temples, baths, a forum, a capitol, and a theater—almost have an enchanted air at times and impressively document a bygone era when this city was an important center of Roman trade for many centuries. It was originally established as a military outpost to control access to the Tiber.