The Schlei (German: [ʃlaɪ] ⓘ; Danish: Slien or Slesvig Fjord[1]) is a narrow inlet of the Baltic Sea in Schleswig-Holstein in northern Germany.
It stretches for approximately 20 miles (32 kilometers) from the Baltic near Kappeln and Arnis to the town of Schleswig.
The important Viking settlement of Hedeby was located at the head of the firth (fjord), but was later abandoned in favor of the town of Schleswig.
A museum has been built on the site, telling the story of the abandoned town.
The current name is thought to have been used only for the inner Schlei (the broads at the top of the firth now known in Danish as the Store Bredning and Lille Bredning and in German as the Große Breite and Kleine Breite, near Schleswig).