Onstaborg, Medieval fortress in Sauwerd, Netherlands
The Onstaborg fortress featured thick walls, multiple strong houses, and a central tower that dominated the landscape of northern Groningen province.
Founded in 1325 by the Onsta family, the fortress faced a major siege in 1400 when Groningen forces captured and damaged its fortifications.
The Onsta family exercised regional governance from this fortress, representing Hunsingo through Folcmar, who served as a regional representative in 1325.
Archaeological investigations between 1996 and 2023 examined the foundations and structural remains of the former fortress site in Sauwerd.
The fortress contained multiple separate sleeping quarters and defensive structures, documented in detail during a 1514 inventory before its destruction.
Inception: 1325
GPS coordinates: 53.29490,6.53120
Latest update: March 6, 2025 17:53
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