Burg Esesfeld, Carolingian hillfort site in Itzehoe, Germany

Burg Esesfeld is a vanished Carolingian ringwall fortification on a Geest spur at the western edge of Itzehoe, near Heiligenstedten. Charlemagne ordered it built in 809 on the Stör; it covered about one hectare, enclosed by an earthen rampart over 6 m high with a ditch in front. Only a few ditch remains survive, the rest destroyed by sand and gravel digging and by the Marschbahn railway line.

Built in 809 AD as the first Frankish fortification in Nordelbien, Burg Esesfeld preceded Hamburg's Hammaburg and successfully withstood a Danish and Abodrite attack in 817 AD during early medieval conflicts.

The fortress served as a crucial base for Christianization efforts in northern Germany, supporting missionary activities after the establishment of Welanao monastery around 822-823 AD in the region.

Archaeological excavations began in the 1920s and continued through the 1980s, though extensive sand and gravel extraction plus railway construction have severely damaged the original site remains.

This fortress represents the earliest Frankish military presence north of the Elbe River, marking the beginning of Carolingian expansion into Saxon territories and Danish borderlands in medieval Europe.