Søby Volde is a well-preserved 11th century rampage north of Søbygård and 5 km south of Søby on Ærø, which was probably built by King Niels (1104-1134) as protection against German expansion in the Baltic Sea. Several Vendean attacks on the Danish population made this type of citizenship necessary.
The castle worked for approx. 150 years, but lost its importance towards the end of the 13th century and declined quickly. The violence itself is still very well preserved and the culmination of the violence is 36 meters above sea level. The offender is divided into three parts, consisting of a trapezoidal edged main bank, a double-necked pit with an intermediate, pointed vault north of the main bank and something reminiscent of a semicircular circumference north of the facility.
Southwest of the scene is Vitsø Nor, which was a regular fjord around 1100. Between Søbyvolde and the bottom of Vitsø Nor, during excavations in 1978 and 2004, traces of a medieval settlement were found, indicating that artisans were present in the 11th century.