Critical Mass: You either do it and love it, or you hate it and like to comment very virulently about how annoying it is. It's celebratory, it's rag-tag, it's kind of anarchist, and yes, it's getting pretty old now that we're 20 years in. But prior to their 20th anniversary ride this Friday, the org has opened a little pop-up "Welcome Center" that's only open 12 to 5 p.m., at 518 Valencia Street (at 16th).

They're selling stuff like commemorative posters, and copies of the book Shift Happens: Critical Mass at 20, edited by Chris Carlsson, LisaRuth Elliott & Adriana Camarena.

And yes, once again, for the (literally) 1000th time, try not get around town in a hurry after 6 p.m. on Friday.

[Uptown Almanac]