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Aggregation No. 1Walk/Ride Day Evening from 5 to 7:30 p.m. Friday at Magazine Beach, at the river end of Magazine Street in the Cambridgeport neighborhood. Free.

Celebrate the end of the week and month as well as the idea of green commuting with music, poetry and maybe a dip in the pool (before 7 p.m.). Bring blankets, beach towels and a picnic dinner to supplement bread donated by Iggy’s and lemonade and other snacks donated and served by Trader Joe’s. There will also be free Clif Bars for participants and a raffle for Kryptonite bike locks. The event – to which you should come via green transportation, obviously – is brought to you by the Cambridgeport Neighborhood Association. Information is here.

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Aggregation No. 2OpenAir Circus at 7 p.m. Friday, at 2 and 7 p.m. Saturday, and at 2 p.m. Sunday at Nunziato Field, at Vinal Avenue and Summer Street, Somerville. There is a suggested donation of $3 per person.

The OpenAir Circus, a nonprofit, community-based program, is ready for its annual showing off of skills its students learned during summer classes. This 30th annual show features children and adult performers in a two-hour circus extravaganza with one 15-minute intermission, and refreshments, souvenirs and circus equipment available for sale. Information is here.

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Aggregation No. 3Roller derby doubleheader from 4 to 11:30 p.m. Saturday, with games starting at 5 and 7 p.m. at Simoni Ice Rink, 155 Gore St., East Cambridge. Tickets are $16 for adults, or $12 for students with valid ID; $5 for kids 6 to 17; and free for kids under 6.

Tickets include admission to matchups between the Arkham Horrors and the Nutcrackers and the Cosmonaughties and the Wicked Pissahs. The Daddy’s Bonetown Burgers and Munch Mobile Kitchen food trucks will be selling during the event. At 9 p.m. comes an afterparty with the Dames at a location to be announced. Information is here.

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Aggregation No. 4Your Friends Fest at 6 p.m. Saturday at Cuisine en Locale, 156 Highland Ave., Somerville. Admission is $10.

This night of live music (by Spo, DCDR, currents, Great News and Psychic Dog), comedy (it’s hosted by The Daley Grimes), art (live painting and an art show, as well as a photo booth) and cool vendors (pretty much too many to mention) is an inaugural event celebrating the local intermingling of the music and art community. Information is here.

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Aggregation No. 5“Stay Clear of the Closing Doors”: The Synapse Solo Art Show from 8 to 11 p.m. Saturday at Kulturez, 36 JFK St., The Garage Mall, Harvard Square. Free.

The artist Synapse spots people on the T, sketches them, puts them on stickers and “displays” them everywhere – including back on the trains he travels. Now his work has been gathered at the Kulturez hip-hop style store for a party and showing, one of the rare art shows you might attend where you’re going to find yourself in what’s on the walls. Information is here.

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Is that too late? Check out “Space, Object & Artifact” from 1 to 5 p.m. Saturday at The Nave Gallery, 155 Powderhouse Blvd., near Teele Square, Somerville, a free show in which artists Kate Benson, Carolyn Latourelle and Emily Manning-Mingle explore what the spaces we occupy and our belongings reveal about us, and how personal objects and places elicit emotional responses from those unfamiliar with them. Information is here.