Hadmar I of Kuenring, who had also founded Zwettl Abbey, had the present castle constructed in the middle of the 12th century in a strategic location overlooking the river Danube.
Hadmar had Kühnring castle constructed and was the first member of the family to style himself "of Kuenring“.
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He was the son of Nizzo (or Nizo) of Krems-Gars, who was burgrave on the Babenberg castles of Krems and Gars.
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He died without issue in the same year and is buried in Göttweig Abbey.