On the Baltic coast just outside the Lithuanian port city of Klaipėda, a remarkable piece of Second World War history is hiding in plain sight. The gun emplacements of battery Memel-Nord are visible from the beach – and beneath the dunes, an entire network of bunkers, corridors and living quarters has survived largely intact.

Klaipėda – Memel in German – was part of Germany until 1919, when it was placed under French administration by the Treaty of Versailles, before being seized by Lithuania in 1923.

It was annexed again by Nazi Germany in March 1939, becoming the last territorial acquisition Hitler made without immediate military conflict. The battery that now bears its name was built in the months that followed.

Built and maintained by the German military between 1939 and 1945, Memel-Nord is, according to historian and museum specialist Dr Titas Tamkvaitis, the only structure of its kind in the Baltic states.

Today it survives as a museum.