Millennium Partners’ topping off ceremony today for its 60-story, $394 million Millennium Tower Boston comes two years to the day that it broke ground for the luxury residential building in Downtown Crossing.

Millennium has pre-sold more than 90 percent of the 685-foot tower’s 442 condos — deals worth $800 million-plus — since sales started Oct. 23. Sales have ranged from $900,000 for a one-bedroom to more than $10 million for a penthouse, according to partner Richard Baumert.