I finally registered in hope of finding people who maybe know the movie I have been looking for for ages...
The movie takes place in a very dry country in the States. I would guess it is Texas or so. The protagonist lives in or visits a small desert town and hears about some rumors of a coming event (or something like that). Searching the vicinity of the town he finds some carvings/paintings in a cave depicting some kind of alien city/huge UFO that is going to land.
And well, in the end it really lands and the inhabitants are not very friendly. As far as I can remember they look like humans with armor or cyborgs with huge weapons or so. The "visitors" came with one or more huge cities the city/cities had a dome or shield and were built upon some kind of structure with landing supports and their leader was marching down some kind of huge ramp, had a big weapon and I think a bald head with pipes leading from his neck/head to his "armor".
Before they did land, they send some scouts who checked the area, oh yeah and this was definitely in color that much I know for sure.
What non American studio could have made such a movie in the 70s or 80s? It definitely was produced in the west.
I watched it as a little kid (thanks dad for the nightmares) in the mid 80s. So it is kinda old.