15720 Ventura Blvd,
is the location of the Milo Janus health spa at Chatsworth. At least on the season 4 Columbo episode, “An Exercise in Fatality”. According to the episode, it comes with an outdoor swimming pool. It is located in Encino.
A web image search of building 15720 Los Angeles easily finds a picture of its modern self 44 years later. The hedges on the roof may be gone, but the trees remain. It has a dental offices, attorneys, a private investigator, and a FedEx. According to Google’s Street View, there are plenty of office space for lease. Maybe, even room for a health spa.