There's a vibrancy to New York City, Chicago and even our sister city, Philadelphia, that can't be felt in Downtown Pittsburgh. That's not to say the Golden Triangle doesn't hum on weekdays with workers and shoppers -- or on Friday and Saturday nights when theaters, restaurants and PNC Park draw robust crowds.

That's not the problem. It's after 6 or 7 p.m. on weeknights when workers have piled into cars, trolleys and buses and evacuated the Golden Triangle. The place goes almost silent.

It's not that New York, Chicago and Philly are considerably bigger than Pittsburgh. The real difference is downtown housing. Each of the others has apartments and condos interspersed among office buildings and shops. Those downtown residents remain downtown after work. They eat there, shop there, play there. They're the city's vitality at night.

Downtown has had a smattering of residences in places like Gateway Towers and the Pennsylvanian. But now, about 1,000 new apartments and condos are planned or under construction, including those in the forthcoming PNC Three tower on Fifth Avenue, the old G.C. Murphy building on Forbes and the former Macy's store at Fifth and Wood.

Even so, 1,000 is a pittance -- and that's what makes the announcement by the Pittsburgh Cultural Trust that it wants to construct 700 condos and townhouses on a six-acre plot within the Cultural District so exciting. The mammoth $460 million development plan, which is to include a 225-room hotel and a park arcing over the 10th Street Bypass to the Allegheny River, will be mostly privately financed.

The Cultural Trust has clearly shown its ability to complete cultural and economic development projects since it was founded in 1984. Its first was conversion of the former Stanley Theater into the Benedum Center for the Performing Arts. That was followed by numerous projects along Penn and Liberty avenues in which buildings were renovated and theaters created.

What was a derelict district in 1980 now gleams. Part of the credit must go to the city's foundations that have faithfully contributed to the Trust's endeavors, including the Heinz Endowments, the Claude Worthington Benedum Foundation and the Richard King Mellon Foundation, all of which helped the Trust buy the six acres for this housing development.

The Trust hopes to break ground for the first phase of the riverfront housing next summer. Before that happens, it must secure financing from both private and public sources. It is negotiating with state, county and city officials for financial support.

Converting Downtown from a collection of vacant buildings and forlorn storefronts into a neighborhood that buzzes both day and night is a good public investment. Just as the foundations have, the governor, the mayor and the county chief executive should endow this project.