Stalker (1979)

My favorite Tarkovsky (I go back and forth between Andrei Rublev and Solaris for second place), about a guide-led expedition into a mysterious area known as only as "the Zone." This one is visually (and aurally) arresting in a completely different way than the similarly premised Annihilation—there are no sci-fi special effects to be found here, but Tarkovsky still conjures up an eerie, otherworldly atmosphere, sometimes out of nothing more than a grassy field in broad daylight.