The owner of U.S. Bank Tower in downtown Los Angeles — the tallest skyscraper in the West — is building an outdoor observation deck, bar and restaurant on the top floors, part of a $50-million makeover of the 72-story building.

The famous building, once packed with prestigious firms, fell on hard times in recent years and was almost half empty when it was bought in 2013. The new owner, Singapore-based Overseas Union Enterprises Ltd., is now detailing planned improvements.

Built in the late 1980s as an exclusive corporate cathedral, the round, crown-topped tower faces fresh competition for tenants from recently renovated historic buildings popular with young Internet companies and other creative businesses. Beyond keeping the building competitive, OUE aims to profit by charging tourists admission.