Photo courtesy of TCC

The grand penthouse at St. Regis Residences Boston condominium tower sold for $23.5 million to the developer of the project.

Developer Jon Cronin said his family is in the process of moving into the 10,000 square foot unit, which spans portions of the top two floors and contains a notable feature: a private swimming pool.

Cronin said a “substantial” custom buildout has transformed the former  “cold, dark shell” in the 22-story tower at 150 Seaport Boulevard.

“That has always been the plan to purchase, since we broke ground [in 2018],” he said.

The transaction was financed with two separate mortgages, one for $18.7 million from Northern Home Loans LLC, and one for $8 million from Northern Bank & Trust, according to Suffolk Registry of Deeds filings.

Another penthouse unit sold this week for $9 million, leaving two penthouses available in the 114-unit building.

In November 2023, Cronin Group refinanced the project with a $240 million mortgage after selling 10 units at a limited-bid auction to accelerate sluggish activity.

Approximately 60 percent of the building’s units are currently sold or under agreement, Cronin said.

Another double penthouse on the 19th floor of the tower sold in July for $20.3 million, the previous high water mark for the building which was completed in 2022 at the former site of two waterfront bars.