Complex sentence: Perhaps the most famous song associated with the facility was "Hotel California" by The Eagles, which was rumored to be about a stay in a mental hospital among residents of Ventura County; but this is most likely not true.
Split into simpler sentences: Perhaps the most famous song associated with the facility was "Hotel California," by The Eagles, which was rumored to be about a stay in a mental hospital. A popular rumor, especially among residents of Ventura County, but this is most likely not true.