BOSTON -- Of the few remaining gilt-era mansions in Boston's Back Bay is for sale for the first time in decades.

The Ames-Webster mansion at 306 Dartmouth Street boasts 26,000 square feet, 50 rooms and 28 fireplaces. The property is also one of very few where architecturally rich details have been preserved.

A mosaic tile entryway leads up to an 18 by 36 foot great hall with rich carved oak paneling often referred to as the most palatial space in the Back Bay. A carved, oak staircase featuring cherubs and seahorses winds up four stories and is topped by a stained glass skylight by artist John La Farge.

A mural entitled the "Justinian Cycle" that surrounds the skylight is the only known mural in the United States by French Painter and academician Benjamin Constant. The Byzantine-style murals are framed by the third floor carved-oak balconies.

The 1872 mansion is one of the largest single-family homes in the Back Bay and has only had three owners in its history.

It is the first time this property has been for sale since 1971. It has been owned by Reality Realty Trust since 1971, whose members include developer Neil (Ted) St. John Raymond, of Raymond Property Co., and the founding members of the architectural firm CBT Architects.

Brokers anticipate the mansion will sell for $18 million to $25 million -- either as a single-family home, multi-family residence or commercial office space.