A Millennium Tower Boston condo unit features marble kitchen islands, Sub-Zero wine fridge and views of the Seaport District.

Life in the Millennium Tower Boston is a study in contrasts, from the clubby residents’ lounge with its marble and wood finishes to the modern living quarters above with floor-to-ceiling windows showing off expansive views of Boston and beyond.

Just 19 of the Millennium’s 442 luxury condominiums are still available, including three penthouses. The largest, a 4,000-square-foot penthouse on the 58th floor, is listed for $12.5 million.

Since mid-July, nearly 90 units have closed with average sales per square foot of roughly $1,500, said Rich Baumert, a Millennium partner. That figure is expected to rise with the completion of the penthouses over the next two months.

Units on the western side of the 60-story tower at 1 Franklin St. in Downtown Crossing sold out soonest, Baumert said, thanks to demand for the vistas of Boston Common, Back Bay and the Charles River. A 3,172-square-foot unit listed for just under $7.2 million offers that perspective, along with three bedrooms and four and a half baths, Sub-Zero appliances and 10-foot ceilings.

Chef Michael Mina oversees the residents-only club room (pictured) and will open the sushi-themed Pabu restaurant in October at the Millennium Tower Boston.

Millennium Partners touts its attention to detail by a staff of 60 on-site employees with a combined 900 years of hospitality experience, led by General Manager Brian Clark who also manages its Millennium Place condo tower on Washington Street. Residents whose first instinct is to reach for their smartphone will gravitate to the tower’s custom mobile app, which enables them to request their vehicle, order groceries from Roche Bros. supermarket or have dinner delivered to their door. Chef Michael Mina, who will open the Pabu restaurant at Millennium in October, will contribute monthly recipes and cooking videos. Mina also oversees the residents-only club room and bar.

Technology also plays a major role in the resident fitness center, where workout machines sync with residents’ Netflix accounts and wearable fitness apps. The resident amenities area spans 23,000 square feet on two floors, including a junior Olympic-sized pool and spas run by Marc Harris salon.

With the nearing completion of the project, Millennium Partners is looking ahead to its next local opportunities.

The company is one of six developers seeking to redevelop a city-owned parking garage at 115 Federal St. into a large mixed-use development. Millennium has proposed a 725-foot-tall office and residential tower.

“Considering there’s only 19 homes left to sell, our Boston team would like something else to do,” Baumert said. “We’ve got our fingers crossed.”