The official opening of Vertex’s new headquarters last week in Boston’s Seaport District is an indication that the once-desolate neighborhood has come a long way over the past few years.

It wasn’t too long ago that the idea of placing a modern 1.1 million-square-foot glass-and-steel building in this previously quiet backwater seemed a little quixotic, even a little crazy.

But the prospect of creating a new city within a city was further propelled by Vertex’s move from Cambridge to Boston. There are few large swaths of land near any city so ripe for development as the Seaport has been.

Joe Fallon, the developer behind the gleaming development, made a bet on Fan Pier and South Boston, and it paid off big time. More companies are moving into the neighborhood, rents are steadily rising – even forcing some companies to look for cheaper rents elsewhere – and hip restaurants and luxury apartments are popping up.

In April, construction will start on the $600 million One Seaport Square, which will have two 22-story towers with 800 apartments and 260,000 square feet of retail space. There are, of course, things missing from the neighborhood: a supermarket and a pharmacy, to name just two. Whether these types of retailers will relocate to the neighborhood remains to be seen, but they come without a market. That market is more apartment and condo dwellers that would make it economically viable for a Whole Foods or Star Market, for example, to locate in the neighborhood. Office workers who commute from other parts of the city or suburbs just won’t cut it.

One Seaport Square is part of the larger Seaport Square project, which will feature 23 acres of development, including 1.2 million square feet of retail, 500,000 square feet of hotel space, 2.6 million square feet of residential and 600,000 square feet dedicated to culture, education or the arts.

All of this is significant for Boston real estate – and a big deal for Boston in general.