Congregation Kehillath Israel
384 Harvard Street
Update. The main event lasted about an hour. The crowd was separated by Harvard St but crossed it all the time, traffic there being slow and carefully directed by multiple policemen and watched by a few black suits. Plenty of people of all ages waving banners, dancing and having a good time. A few speeches, as usual. After the event, participants were walking here and there, talking and laughing, and leaving tons of money in the neighborhood restaurants. An open convertible with a Maine plate was cruising around with a huge flag of Israel. (I myself had a small flag, given to me by a friend in Haifa, attached to my car.)
I also saw one protester. He was not engaging in a real counter-protest, but rather holding a sign, sort of "war is not an answer". He had a low-key discussion with a few of the participants.
The whole thing was pretty enjoyable, despite