Paul Allen, the billionaire co-founder of Microsoft, is listing one of the largest undeveloped parcels left in Beverly Hills—a sprawling 120-acre development site known as “The Enchanted Hill”—for $150 million.

Mr. Allen had planned to develop a private compound there, but didn’t get around to it, according to Zach Goldsmith of Hilton & Hyland, one of the listing agents. The property has five flat lots which could be used for development. For example, a new estate could include a main house plus guesthouses, a winery and...