A few meters from the same spot where Bassie & Adriaan previously drove the Matra Simca Rancho in ''The Secret of the Key'' and at the tunnel where Adriaan jumped on the truck of the Plaaggeest. There is this entrance on the Kortebuurt in Maassluis where they had to turn right with the Baron's red Fiat Panda in the Verdwenen Kroon!
Finally found after always being unknown thanks to fan Maurice van Oort.