To fill vacancies, Blackstone Group LP, the biggest U.S. office owner, is going after startups and their armies of twentysomething workers. In Flaherty’s building, 100 Summer Street, Blackstone has installed a private club on the second floor open to employees of companies in the building, with beer and wine taps, a gym with private showers, arcade games, foosball, and baristas who finish off cappuccinos with foam artwork. It even has a startup-style name, Assemblyon2. “Having a cool office when I was a kid meant you worked at Google,” says Flaherty, who is on the sales force at Rapid7, a cybersecurity company. “Among my friend group, this is now the coolest office.”

Companies in every industry, from autos to retail, have been scrambling to adjust to millennials’ tastes and expectations, and commercial real estate is no exception. Blackstone, Brookfield Property Partners LP, Boston Properties, and other big landlords are spending millions to inject Silicon Valley playfulness into aging towers in big cities. They’re in an arms race against new construction and co-working businesses such as WeWork Cos. “The way towers were built in the 1980s, they were a monument to the corporation,” says Lisa Picard, chief executive officer and president of Equity Office, a Blackstone unit that owns office buildings. “Now, if it feels corporate, that’s the kiss of death.”