Boston-based Marcus Partners has acquired the 45,000-square-foot Horticultural Hall at 300 Massachusetts Ave. and plans a multimillion-dollar capital improvement program.

Changes to the 1901 Beaux Arts-style building will include lobby renovations, new entrances and mechanical upgrades, Marcus Partners said in a statement.

Marcus Partners signed a 99-year ground lease with the First Church of Christ Scientist on May 31 and Cambridge Savings Bank granted an $11.5 million mortgage, according to Suffolk County Registry of Deeds filings.

“Tenants are increasingly being drawn to this corner of the Back Bay, with the dramatic renovations occurring on the adjacent Christian Science Plaza, the arrival of the new Four Seasons Hotel, Flour Bakery, the vibrancy and energy created by the adjacent institutions all really differentiate this location as a magnet for creative and tech companies,” Pete Cameron, a principal with Marcus Partners, said in a statement.

Marcus Partners said it’s open to a “wide variety of users” including office, retail and institutional space at the National Historic Register property.

First Church of Christ Scientist acquired the property from the Massachusetts Horticultural Society in 1992 for $1.6 million.

“We are pleased to have a new neighbor and we look forward to improvements planned for the interiors of this historic and distinguished building,” Ingrid Peschke, a church spokeswoman, said in a statement.