You can tell a lot about a city by the way people use its parks. Not the tourist parks, but the parks locals use to the hilt, the ones with flea markets and music and playgrounds — in this case, a crazy wooden structure with ropes to balance on. Sundays in the summertime, Berliners flock to Mauerpark. They paint, they play, they recline on the grass. They drink a lot of beer. They smooth each other’s auras. They play soccer with empty plastic bottles and, when the sun goes down, they dance to boom boxes pulsing fast German techno.