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Gym Fitness centerAbout the Club
Mass Underground South Boston is a gritty, community-driven gym built for people who refuse cookie-cutter fitness. Unlock the door with your phone any time between 4:30 AM and 10:30 PM for access to free weights, plate-loaded machines, turf, and cardio rigs. When the work’s done, recover in our saunas and ice baths. Stash your gear in secure lockers, freshen up in the bathrooms, and grab some free cold brew on your way out. We offer free, limited parking in MU-marked spots, and there's also street parking nearby. Join a crew that pushes, supports, and inspires you to become the greatest version of yourself.
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Reviews
Terence S
★ 5
Great set up, Clean and a comfortable atmosphere to work out. Highly recommend memberships.
Source: Google
Mark Smith
★ 5
Mass Underground is easily one of the best training environments around. The moment you walk in, the energy is different — the music, the atmosphere, and the community make you want to push harder every time. The coaching is top-notch; they’re hands-on, they actually correct your form, and they know how to get the best out of you without ever making it feel overwhelming.
The workouts are challenging but super rewarding, and they’re structured in a way that keeps you improving week after week. You can tell there’s real intention behind every session. What really stands out, though, is the culture. Everyone is supportive, welcoming, and genuinely invested in getting better together. It’s the kind of place where you walk out feeling stronger, clearer, and in a better mood than when you came in.
If you want high-level training without the ego or intimidation you find in some gyms, Mass Underground is the place. Truly a standout fitness community.
Source: Google
Connor Hebert
★ 5
Best gym I’ve ever been a member of. Has a perfect complete setup with everything g you need and nothing you don’t need; No need for the flashy bells and whistles. Just grade-A equipment, sauna and cold plunge. This is the perfect gym for weightlifters who want to take good care of their bodies. Great atmosphere and great staff and crew to compliment the gym itself. Fully recommend!
Source: Google
Christopher Longo
★ 5
Did a 6 month membership at this gym and it was AMAZING! All of the machines and equipment were state of the art and easy to use. Not to mention the amenities are a huge plus. Definitely recommend if you are living on the east side of Southie.
Source: Google
Shane Feichtinger
★ 5
I’ve been staying in Boston over the summer and wasn’t satisfied with the campus gym available where I’m staying. Found this place at the end of June and got a one month pass. Great equipment, lesser wait times, friendly gym goers, and super easy cancellation. Would definitely go again if I’m ever back!
Source: Google
Justus Goldmann
★ 5
Great, and in my backyard!
Source: Google
Vincent Troisi
★ 5
Source: Google
Michael Messier
★ 5
Hands down best gym in South Boston.
Saunas, cold plunge, brand new machines… can’t find a better spot in the city.
Source: Google