Last week, though, the project started picking up. Way up.

Crews erected an enormous construction crane, hoisting one blue gridded section atop another, heading for the heavens. Neighbors and passersby gathered to watch it go up.

What we're seeing is the future.

Greenbridge and the still-to-come Lot 5 project a few blocks east represent the town of Chapel Hill's push to breathe new life into downtown. Both projects will consist mostly of upscale condominiums, supplemented by a handful of affordable units, with some commercial space on the ground floors.

Both projects reflect some basic principles that guide growth in the early 21st century. Density is a virtue. Focus residential growth in urban centers. Build up, not out (the taller of Greenbridge's two towers will stand 10 stories and 128 feet, about 60 feet lower than the construction crane).

The basic idea is that by putting a lot of new homes in compact areas downtown, you pump an infusion of new people into the area. Your sidewalks become bustling and safe. Restaurants, shops and nightspots thrive, and new businesses clamor to move in and join the fun. Downtown becomes a vibrant environment for residents, and lots of visitors come to enjoy the vibe and fill local coffers.

That's the picture painted by supporters of the new projects, anyway. What's not to like?

There are potential downsides, though. Gentrification, for one. It's likely that the expensive new projects will increase pressure on the nearby neighborhoods such as Northside, making it ever more difficult for people of moderate means to be able to afford to live there. Housing costs in Chapel Hill already are out of reach for many. Do a few tiny affordable condos outweigh the potential long-term decrease of economic diversity in the surrounding neighborhoods? Are we hastening the day when only the wealthy can afford to live here?

We've been talking about these issues and these projects for a long time. But until now they've always seemed sort of abstract and theoretical, some distance in the future.

Well, the future is here. Greenbridge is going up -- we can see it right outside the window -- and soon enough Lot 5 will follow.

Mayor Kevin Foy and the Town Council think these projects will serve as a spur to new energy downtown, new vitality and excitement. For everyone's sake, we hope they're right.