Perched on prime Charles River real estate, on the edge of Harvard Square, the monastery offers unexpected sanctuary. Thick, stone walls muffle traffic noise and create an architecturally-inspiring place. The blend of Italianate and Romanesque design, the arches everywhere, evoke an older time and place. And most unexpected, the monastery is vibrant and engaged with the world outside.

The Society of Saint John the Evangelist (SSJE) welcomes guests with what one frequent visitor called “radical hospitality.” For the Episcopalian monks who live at the monastery, that means listening attentively, providing spiritual direction, and sharing prayer and meals with visitors. For overnight guests, that often translates into a retreat where days follow a slower rhythm, where they find a calm environment for reflection on life and religion.

“It’s really a place for me to recharge,” said Lucas Fleming, 50, a criminal defense lawyer from St. Petersburg, Fla., who visits at least once a year. “I can download all the stress that I’m under and I come out feeling a lot better, a lot more relaxed. I liken visiting the monastery to doubling your vacation time. If you go for three days, it feels like you’ve been gone a week. When I’m there, I feel myself functioning at a much slower pace, a much more intentional pace, a much more meaningful pace.”

Stepping into the guesthouse, something about the simple decor — the dark trim against white walls, the oriental rugs, the original hardwood floors — is warm and welcoming. It feels like someone’s home, albeit a very quiet home. Not far from the main entrance, the first-floor common room features a fireplace flanked by two windows with river views. A sign on a coffee table reads: “We ask that you please respect the silence for which many guests come on retreat.”

The same request appears throughout the guesthouse and sets the relaxed, contemplative tone. To use cellphones, guests step “off campus,” outside the monastery’s fences.

The guesthouse has 13 single rooms for overnight visitors, including a handicapped-accessible room on the first floor. Named after saints and apostles, the rooms are small and minimalist. Accommodations include a bed, bureau, chair, desk, closet, sink, and window overlooking the river in a narrow, roughly 60-square-foot space. Decorations include crosses and icons. Both the second and third floors have four bathrooms for guests to use. On the lower level  there is a dining room, a kitchen for making coffee and snacks, and a small chapel used mainly for meditation.

The monastery suggests donations ranging from $100 per night for individual, self-guided retreats ($50 for students) to $125 per night for companioned or group retreats ($65 for students). During a companioned or group retreat, a brother at the monastery is available for spiritual guidance and one-on-one meetings. Generally, visitors stay two to four nights.

Each year, approximately 1,000 guests stay at the monastery in Cambridge, while another 500 go on retreats at Emery House in West Newbury. Emery House is the SSJE retreat center that offers lodging in hermitages and rustic cabins, in addition to rooms in a main house. To accommodate guests on retreat and maintain the brothers’ ministry, the monastery and Emery House, SSJE relies on charitable donations from individuals. Guest donations cover roughly 10 percent of the SSJE’s annual budget.

Guests come from all around the world and all walks of life: men and women, students and lawyers, teachers and bankers, social workers and real estate agents. They are not all Episcopalian, nor all Christian. While some visitors are ordained, most are not members of any clergy. Still, as Brother Jonathan Maury said, “The one thing that kind of unites everyone is that they’re seeking God in some way or other.” That may mean attending daily religious services at the monastery or sitting in silence in the guesthouse common room or walking through Harvard Square or heading to Fenway Park. Visitors are free to follow their own schedule and go wherever they want outside the monastery, though many structure their stay around daily services and meals with the brothers.