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Aggregation No. 1Somerville Open Studios from noon Saturday to 6 p.m. Sunday throughout Somerville (with some artists opening their studios in a preview event from 6 to 9 p.m Friday. Free.

The 18th annual Somerville Open Studios has more than 350 artists throwing wide their doors to more than 90 workshops and studios for public perusal (see the map here). A good guide is here – including an Artists’ Choice Exhibit at the Somerville Museum and information about Somerville Community Access Television’s free 7 to 9 p.m. Saturday outdoor film festival in Union Square (with 15 locally made short films and local food vendors selling treats). While much of the fun is traveling from studio to studio to see how artists work, one way to get lots of variety in a short time is to stop into group shows such as at The Center for Arts at the Armory, 191 Highland Ave., where there are displays for everything from Hiroshi Minato’s contemporary men’s jewelry to George Teshu’s ecstatic paintings of women (seen above) and Laurinda Bedingfield’s abstracts on wood. The Armory also hosts an exhibit of kids’ art. Information is here. (Interested in a different kind of art? Check out Public/Private: Art at MIT, a free 2 to 3:30 p.m. Sunday guided tour of artworks by renowned contemporary artists – including Dan Graham, Lawrence Weiner, Sarah Sze and more – across the Massachusetts Institute of Technology campus. Just RSVP here.)

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Aggregation No. 2MASSDestruction Robot Competition from 8 a.m. Saturday to 5 p.m. Sunday at Artisan’s Asylum, 10 Tyler St., in the Spring Hill neighborhood of Somerville, between Porter and Union squares. Tickets are $5 at the door.

Before Skynet becomes self-aware, we still get to pit robot against robot in combat for our pleasure. Stop in to the custom-designed Cochran Combat Corral to see the carnage among robots of various weight classes (most too small to seem menacing). Information is here.

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Aggregation No. 3Taza Chocolates’ annual Cinco de Mayo Block Party from 1 to 5 p.m. Saturday at Taza Chocolate, 561 Windsor St., between Inman and Union squares, Somerville, or 21st Annual Harvard Pow Wow at 1 p.m. Saturday in Radcliffe Yard, between Brattle and Garden streets west of Harvard Square. Both free.

Taza Chocolate’s unofficial welcome party for spring returns, shutting down the block in front of its factory for an afternoon of food (with chocolate to sample, of course, but also Somerville Brewing/Slumbrew and Bantam Cider products in a beer and hard cider garden, food from Taco Party, The Happy Taco, and Tex Mex Eats and dessert from Scoopsies Ice Cream) and celebration and music from DJ Trizlam. Products from high school entrepreneurs at The Possible Project will be on sale, including new Taza merchandise. Information is here.

For a more serious celebration with indigenous people’s the Harvard-hosted annual pow wow will be at the Radcliffe Institute for Advanced Study, led by a committee of Native American students from the college and graduate schools and featuring singers, artists and dancers from the Harvard community, Greater Boston and from tribes across the United States and Canada. The grand entry is at 1 p.m. Information is here.

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Aggregation No. 4Black Market art/flea/record/artisan market from 11 a.m. to 5 p.m. Sunday at the Cambridge Community Center, 5 Callender St., in the Riverside neighborhood, or Club Passim Benefit CD and Vinyl Sale from 11 a.m. to 4 p.m. Sunday at Passim, 47 Palmer St., Harvard Square. Black Market asks $1 at the door to help cover the cost of the space; the Passim sale is free.

This one-day event has seen everything from secondhand to handmade including artwork, zines such as the standout Okay Mag, records, body care, baked goods, books, patches, pins, T-shirts, leather goods, knits, woodwork, pottery, vintage clothing, jewelry, tea and haircuts, with a staggering array of vendors. (The cross stitch patterns of watercolorist Lierre Kandel is above.) Information, including a list of the more than 80 artists and businesses signed up to sell, is here.

Meanwhile, Passim is holding a third CD and Vinyl Sale after a successful winter event that just brought more donations. There will be food and drink tastings as well, and proceeds from the event go to Passim and its community music programs. Information is here.

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Aggregation No. 5The 33rd Annual Mayfair from noon to 6 p.m. Sunday in Harvard Square. Free.

This spring tradition features four stages of music; more than 30 dance troupes; more than 40 food vendors serving international fare and local favorites; more than 120 artisans and merchants selling arts and crafts, jewelry and vintage clothing; a Church Street chalk art event that raises money for local charities; Cambridge Historical Tours and and “Stump the Historian” game at the history booth; and games and entertainment for all ages, including an all-ages Roaming Railroad train ride and children’s activity area, aerobic bootcamps and four beer gardens. No wonder the event draws more than 100,000 people. Information and a complete schedule of music and other events is here.

Update on April 29, 2016: MayFair will be postponed to May 15 due to inclement weather, the Harvard Square Business Association has announced.