Separated during the Cold War like a pair of pining lovers, the west and eastern portions of the rail ring around the city were rejoined in 2002. Start at any station and take it in any direction (S41 clockwise, S42 counterclockwise), and you’ll wind up back where you started in about an hour. You watch east become west, become east, become west, as smokestack skylines blend into shopping centres, replaced by Communist Plattenbauten, forests, and back again.