Chęciny Royal Castle was built in the late 13th century in Chęciny, Poland. It fell into ruin in the 18th century and remains in that state to this day.
Wikipedia https://en.wikipedia.org/wiki/Chęciny_Castle
Official Website http://zamekcheciny.pl/
Address Radkowska 4, 26-060 Gmina Chęciny, Poland
Coordinates 50°47'50.645" N 20°27'38.405" E