U3 (Hamburg U-Bahn) ยท Relations URL: https://knowledge.ivjn.us/en/concepts/ubahn-hamburg-u3/relation.html The U3 is the 20.7 km long ring line of the Hamburg U-Bahn with 25 stations; the first sections were opened in February 1912, and it operates as a ring between Barmbek and Barmbek with a branch line to Wandsbek-Gartenstadt. Page 1 / 0, 0 total