The National Historic Landmark is now a 300-room hotel with views of the Charles River. (Liberty Hotel)

After housing inmates since the 19th century, Boston's former Charles Street Jail now hosts hotel guests.

Completed in 1851, the Boston Granite Style building had been empty since 1990. The National Historic Landmark opened on Sept. 5 after a $150 million project.

"It really was a deteriorating hulk of granite, full of storage stuff," says Gary Johnson, principal architect at Cambridge Seven Associates. "It was dark and dank, with pigeons flying around, and I thought, wow, what a magnificent space."

In addition to adapting the original cruciform structure to become the new Liberty Hotel, architects added a 16-story tower for guest quarters. The new tower uses the style elements of the old building, such as window patterns and lintel beams. In contrast to the granite structure, the tower is made of contemporary materials, such as iron spot brick and glass.

"During restoration, we discovered this huge space with beautiful soaring windows," says Kristen Hammer, spokesperson for the hotel. "We pulled that design element into our plans for the new addition."

The entrance to the Liberty Hotel is the storage space of the old jail. Guests walk down a short corridor with an eight-foot ceiling before entering the atrium to look up 90 feet and stand beneath the cupola on the top of the hotel. Far from the musty room Johnson entered in 1999, the atrium is now decorated with tile mosaics and tapestries.

"It's more than restoration or adaptive reuse," Johnson says. "It's total transformation."

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