This luxury residential property is on the market for $18,000,000.

Built in 1908 by architect William A. Boring, the Beaux Arts landmark was formerly run as the St. Agnes Boys’ High School.

In 2014, it was sold to architect/developer Cary Tamarkin, who converted the historic building into a collection of thirteen high-end residences.

“555 West End Avenue is driven by amazing historic architecture, spirit, and light—all the pillars that New York’s greatest buildings have been built on,” says Cary Tamarkin, the founder and chairman of Tamarkin Co.

“These homes are certain to resonate with buyers who appreciate authentic design and are looking for the experience of a private mansion but with the ease of condominium living in a prime Upper West Side location.”

The Solarium Penthouse is its crown jewel, located in the Catholic school’s former gymnasium—and the luxury residence comes with its own home gym, too.

The 3-bedroom, 3-bath penthouse features a striking ‘Great Room' with 19-foot arched ceilings and a full glass wall, opening out onto a large outdoor terrace for alfresco dining and entertaining.

The luxury residence offers a clean, contemporary design which aligns with the space’s soaring ceilings and open-concept living spaces, featuring high-end finishes throughout, like hand-crafted, white fumed oak kitchen cabinetry by Christopher Peacock with Arabescato slab marble counters and slab backsplashes in the gourmet kitchen.

Located just one block from Riverside Park, 555 West End Avenue is the Upper West Side’s answer to Park Avenue.

All photos belong to the listing agency.