The city has filed a $1 million suit against a man trying to sell priceless old Parks Department architectural drawings.

New Jersey real-estate developer Sam Buckley said he inherited the watercolors from his father, who’d found them in a trash bin more than 50 years ago. The city found out about the whereabouts of the drawings last month, after Buckley handed over 86 of them to Christie’s for a possible auction.

“The Drawings were created for the city, stamped ‘Department of Public Parks,’ and labeled with a case and map number for repository storage,” the suit says, but at some point, they “were either lost or erroneously discarded.”