Älvsborg Fortress built
1360 CE.
Shown on the map at 57.690°, 11.907°.
Älvsborg (lit. 'river stronghold'), now generally known as Old Älvsborg (Swedish: Gamla Älvsborg) or Älvsborg Castle (Swedish: Älvsborgs Slott) to distinguish it from the later New Älvsborg and Älvsborg Fortress, was a medieval castle situated on the rocky outcrop known as Klippan, on the south bank of the Göta Älv river within the urban area of the modern city of Gothenburg. It was demolished in the late seventeenth century, but some of its ruins are still visible today, close to the southern pylon of the Älvsborg Bridge.
Text from the Wikipedia article Old Älvsborg, licensed CC BY-SA 4.0.