Where was Colossus and the Headhunters filmed?
1963 film by Guido Malatesta
Colossus and the Headhunters (1963) was filmed in Ljubljana, 1 place named in its Wikipedia article's Production section, in Slovenia. Wikidata records no filming location for it at all, so the article is the only recorded source. Each place says where its claim comes from.
Places per Wikipedia's Production section
Wikipedia’s Production section names 1 place. Each links to the sentence that says so.