Construction has begun at The Merc at Moody & Main, a new mixed-use project by Newton-based Northland Investment Corp. in downtown Waltham.

The project consists of 269 new residences in three five-story buildings on a 4.5 acre site, along with more than 27,000 square feet of retail space, a 300-car parking garage and 92 surface spaces.

The first phase of residential development is scheduled to be ready for occupancy next summer, with full buildout by 2016.

The project, whose name references the Mercantile Building which once stood on the site, is a block from the MBTA commuter rail station and near an MBTA Express bus stop.

"Waltham’s downtown is a prime location convenient to regional transit and we are very excited to be a part of this new chapter in the city’s history and its future," Peter Standish, senior vice president at Northland, said during a ceremony Thursday.

Buildings will have masonry facades. Residents will have access to a roof deck, outdoor courtyard and patio, library, clubroom and fitness center.