PARKing Day from 8 a.m. to 6 p.m. Friday around Cambridge. Free.

Fifty-five groups will transform more than 120 parking spots into other uses for the day in this global exercise in imagining life with more space for people because less space is needed for cars. In addition to mini-parks and lounges devoted to snacks, library card sign-ups, bicycle tune-ups, projects such as creating customized art helmets and even dance and exercise, the day also celebrates the city’s new bike lanes, informs about co-working spaces in Central Square and wildlife in Cambridge and offers a chance to try out technologies being developed in the community. A complete guide, viewable as a list, map or media, is here.

Danehy Park Family Day from 11 a.m. to 4 p.m. Saturday at Danehy Park, 99 Sherman St., in Neighborhood 9 just east of Fresh Pond. Free.

This 22nd annual event includes music and other performances at a children’s stage, roving performers, children’s amusement rides and arts and crafts, as well as free hot dogs, chips, sodas and T-shirts (while supplies last). The event, sponsored by the city, attracts more than 4,000 people annually. The 55-acre Danehy Park can be reached by the 74 or 78 bus from Harvard Square; the 83 bus from Central Square; or by shuttle buses from locations including the Alewife MBTA Station. Picnics and lawn chairs are encouraged, and the rain date is Sunday. Information including times and locations for shuttles and an event schedule is here.

EMFest from 2 p.m. to midnight Saturday at Out of the Blue Art Gallery Too, 541 Massachusetts Ave., Central Square. There is a suggested $10 donation that will be donated to the gallery so it can keep its doors open through an upcoming planned relocation.

This music and art festival showcasing the creative work being done in Cambridgeport’s EMF Building (also known as The Sound Museum Cambridge) front-loads the acoustic acts, followed by full bands. Over the 10 hours there will be sets by performers including Facc-Tones, Man Trouble (above), Miele, PowerSlut, 2D V, Brett West, The Sound Down Cellar and The Silver Mirrors, as well as film art by Steve Onderick. Information is here. (Also this weekend is the Your Friends Fest 2017 from 6 p.m. Saturday to 1 a.m. Sunday at Once Lounge + Ballroom, 156 Highland Ave., Somerville, a collection of artists, makers and local vendors for $12 in advance or $15 at the door; and a Black Market hosted by Boston Hassle & Ignore Rock ’n’ Roll Heroes from 11 a.m. to 5 p.m. at the Massasoit Elks Lodge, 55 Bishop Allen Drive, Central Square, where a $1 entry fee provides access to dozens of vendors selling cool stuff.)

Cambridge Discovery Day from 9:30 a.m. to 4:30 p.m. Saturday. Free.

Celebrate city history with a day of tours and events, including looks through the Longfellow House-Washington’s Headquarters National Historic Site and Fresh Pond Reservation; a crash course in the secret history of Cambridge’s saloons and speakeasies; explorations of James Russell Lowell’s Brattle Street; inspiration from stained-glass windows at Saint Peter’s Episcopal Church; the delight of architectural gems atop Avon Hill; and more. (The Cooper-Frost-Austin House, 21 Linnaean St., built in 1681, is the city’s oldest house.) The day culminates in the final public art exhibits from “Common Exchange: Public Art on Cambridge Common,” including an interactive park bench, a people’s monument, special banners, a performance cart and an eyes-closed tour of Cambridge Common at 2 p.m. A schedule of events and where to meet your guides is here, and other information is here.

14th Annual Revels RiverSing from 5 to 7:30 p.m. Sunday in Harvard Square and by the Weeks Footbridge along the banks of the Charles River. Free.

Cambridge’s traditional sendoff to summer and welcoming of the months of foliage, Halloween, apple cider and hot chocolate is here, led as it has been for the past decade by the nonprofit Revels organization. It includes the RiverSing Chorus of adults and children, children from the Boston City Singers, a folk band with Ken Field and Stan Strickland on saxophone and the raucous JP Honk! band. Acrobats and street performers will keep things lively and giant puppets and the magical butterflies of Gabriel Q will add to the magic. It starts with a 5 p.m. gathering in Winthrop Park for family festivities. At 5:45 p.m. comes a parade to the Charles River for 6 p.m. singing and poetry along the Charles. Information and printable lyrics – many audience members sing along – are here.