We sat down with Nelson Mills, CEO of Columbia Property Trust, one of the largest office REITs in the country, at the St. Regis, during the big ULI meeting in San Fran this week. (Look to the immediate left of his head and you'll see former S.F. Mayor Willie Brown at the packed bar.) Being the recent winning bidder of the historic New York Times Building—a highly marketed 500k SF asset—was helped by Columbia's great relationship with the seller, Blackstone, he tells us. NYT occupied the tower until 2006, and it’s been filled with tech tenants like Snapchat and Yahoo since. Soon Blackstone and Columbia will be partners; Columbia is selling Blackstone a 49% stake in its Market Square DC property in a deal expected to close this week.

Above, the NYT Building at 229 West 43rd. Their buyer-seller relationship with Blackstone may come in handy this year; Nelson's got his sights set on expanding in West LA, where Blackstone is selling its big portfolio. He says "nothing is hotter" in the whole country than SoMa, which is just where our interview took place. He says he had good timing on picking up SoMa's 221 Main a year and a half ago (when rents were $36 gross and he underwrote them at $55). Further north, Columbia owns 650 California St and 333 Market St.

Competing for properties in S.F. has been hard, Nelson says, and Columbia's been in the best and final half a dozen times before being booted out of the running for properties like 201 Spear and 685 Market. With a recent announcement of another $1B in transactions, today two-thirds of the value of the portfolio is in four high-barrier markets: S.F., Manhattan, DC and Boston.

Since late 2011, Columbia has undergone a dramatic transformation virtually unheard of among publicly traded REITs. Back then, only 38% of Columbia's portfolio was in CBD locations and only 55% multi-tenant properties. Today, nearly 70% of the portfolio is in CBD locations and 79% of the portfolio is multi-tenant. Single tenants are great but not only are they a big single risk but they hold most of the negotiating power when it comes time to renew. "They know you don’t want a 500k SF building back."

Columbia's visibility at ULI this year is high; it scored the back cover of the official program, pictured. This year Nelson will be speaking at Bisnow's BOLD conference in NYC on Dec. 1 (register here).

The biggest challenge a REIT has today is the difficulty of competing with private capital from all over the world. Nelson's got three assets on the market right now: 100 East Pratt (T. Rowe Price HQ building, pictured); 80 Park Plaza in NJ (the PSEG building); and Cleveland’s premier office tower Key Center ("if you're going to be in Cleveland, that's the building to own"). Those three should generate $600M to $700M that'll get rolled back into his target markets.