A climb to the top of the Vienna Metro parking garage yesterday gave me pause. And not only because I was winded from the steps. It was because of what I saw from that perch. The long-planned retail and housing development beside the Vienna station is finally underway. Urban density is coming.

I have mixed feelings about urban density. I appreciate the efforts of Robert E. Simon (founder of the planned community, Reston) and other urban pioneers who have envisioned new ways of living in the suburbs. (In Simon’s case, it was to create European-style “new towns” in the middle of Virginia hunt country; his experiment has been only marginally successful.) And yes, it is true that our long driveways and wide lawns, our streets without sidewalks, do not foster walking or biking. They keep the automobile king.

But from my vantage point yesterday all I could see were bulldozers and barren soil stripped of grass and trees. The price of urban density is suburban leafiness, the openness and beauty that drew us here in the first place. But up there on the fifth level of the Metro Parking Garage, the future was clear: The way out is to build up.