Christianshavn Torv rail
A low rail - ca. 10 meter long - slightly slanted. You need some plywood to make a good run-up. Go there on weekends, where the traffic isn't that crowded. Especially the bikes can be a pain.
At the Christianhavns torv. Take the metro to Christianshavn station. Go torwards downtown - towards the bridge (knippelsbro)… ca. 100 meter from the station.