Well, Spain sure has hidden relics gathered by the Inquisition, and the german Gondor Legion may have had covered up archeologists commissioned as military advisors. At least that's the lineout I planned but never worked out.
Then there could be cursed burying sites from the Punic Wars, descendants of Visigoth cannibals, underground heretic Saracen cults.
Or think an alternative Hemingway's For Whom the Bell Tolls but instead of an Englishman connecting with the resistance to blow up a bridge something really sinister it to be stopped.
Not to mention if they would have to retreat to the mountains and encounter a hidden village inhabited by halfbreed cultists.
Coincedently, yesterday I finally found this NewRay plastic russian MIG airplane toy after searching for at least two years. I was looking for it to use as a crashed republican plane where everybody is looking for.