The Niederelbe (i.e. Lower Elbe) is a 108 kilometers (67 miles) long section of the river Elbe, from western Hamburg downstream to its mouth into the North Sea near Cuxhaven. Starting at (or Elbe kilometer 634) near Finkenwerder, Hamburg, it gradually widens from 2 km (1.2 mi) to 18 km (11 mi). Once passing the Hamburg state border, the Niederelbe also forms the border between the states of Lower Saxony and Schleswig-Holstein.