In dense urban environments, desirable real estate is measured vertically and not just horizontally. I never realized quite how tenacious this maxim is until I took a tour of Union Square with a guide who pointed out all the place-sitting buildings around the square.

What do I mean by place-sitting? Take the McDonald's (hidden behind the scaffolding) in the picture. It does a good business, I imagine, but it's nothing like the business it could do if a real estate developer saw the tantalizing amount of space it has above it. In other words, what McDonald's does inside its store is immaterial. It's just sitting there, waiting for someone to come along and buy it out, called by the possibilities of filling all that air space above it. Burgers and fries can't trump real estate values, especially in the very attractive market Union Square presents at the moment. The same is true of the North Fork Bank space at the north end of the park, and, probably, Zen Palate at the east end. It certainly was when a real estate company bought out the one-level discount store at the corner of University and 14th, across from Lantern's office. It's in the process of putting up a nine-story luxury condo building. Watch those spaces!