The 606-foot-tall residential tower planned for the vacant Filene’s lot in Boston’s Downtown Crossing will be "striking" and "contemporary," says developer Millennium Partners.

Millennium released an "initial description" of its $615 million project, which includes the restoration of Filene’s Burnham Building, Monday.

"The project intends to present the simultaneous and harmonious pairing of new and old, and will consist of uses that will ensure a vital, 24/7 city-sector," Millennium said in a prepared statement.

The 1.3 million-square-foot development will be called Millennium Tower/Burnham Building. It will include 500 condo and rental units, 230,000 square feet of retail space, 200,000 square feet of office space and underground parking for 525 vehicles.

An environmental impact study of the proposed development is underway, Millennium said, and results are expected to be ready for public review and comment within 60 days.

Millennium is in the process of building a 15-story, $220 million residential building at the intersection of Avery and Washington Streets. That project is expected to open in the fall of 2013.