The term "börde" has a twin meaning here. Administratively it refers to a former juridical district and agriculturally to a fertile lowland.
Historically-administratively the Soest Börde comprised the former territorial lordship of the town of Soest in the present municipalities of Soest, Bad Sassendorf and Welver. From a natural regional perspective, it belongs to the Hellwegbörden, whose eponymous centre it represents.[1] Within the natural region classification, however, the Soest Börde, is not recognized as a unit. Instead the sub-regions of the Soest Upper and Lower Börde are used, the boundaries of which are not the same as the borders of the historical Soest Börde. The boundary between the two sub-regions runs just north of the Hellweg.
Wikimedia Commons has media related to Soest Börde.
Natural region maps from the 1:200,000 map sheets by the Bundesinstitut für Landeskunde – the sheets that are mainly relevant here are nos. 542.12 and 542.22.