Here's the high concept: Real estate developer S.L. Green says it'll provide New York City with $210 million in urgently necessary East Side subway improvements -- provided the city lets it build a huge 1,400-foot-tall office tower on the west side of Grand Central Terminal in one of the most densely packed places in the galaxy.

We hope the city agrees. The land-use review procedure for 1 Vanderbilt started Monday -- seeking comments from workaday residents, transit professionals, planning gurus and project neighbors. A decision is expected in perhaps seven months. And while some questions demand detailed answers, the deal's essential outline is positive. The MTA needs to ensure to work toward the best project possible.

Its biggest selling point? That one's easy. In return for an OK to build far beyond the city's height limits, S.L. Green would invest $210 million in the packed, grungy Grand Central subway station to replace staircases, make the Times Square shuttle easier to find and use, and provide access to the long-awaited Long Island Rail Road's East Side Access line, among many other things. The city would not allow Green to occupy 1 Vanderbilt until the station improvements are done.

But isn't a 1,400-foot-high tower a bit much? Not necessarily. When finished, it would be the second-tallest office tower in New York -- outdone only by 1 World Trade Center at 1,776 feet. But with creation of a more modern transit network in midtown, bigger could be far better. At the moment many buildings in the east midtown commercial district are growing old and outdated -- too small for today's sprawling office demands and too old to handle the crushing push of modern electronics. If we want to keep up with Hong Kong and London, we can't rely on the city we built several generations ago.

Many regard 1 Vanderbilt as the vanguard of a push to bring midtown east up to global standards. We hope it is. The vitality of Manhattan has always relied in large part on an egalitarian transit system and a booming real estate market. There are many specific questions to ask about 1 Vanderbilt. But what we've seen is a fair start.