These days, making a landscape appear as if it were inside a jar would typically be relegated to Photoshop. In the past, it was done by the use of double exposures. In a double exposure with analogue, you’re shooting twice without advancing the film. So, you’re basically adding one photograph on top of another (like Photoshop’s “Add” blending mode).
But there’s really no substitute for doing it in-camera. You can do this with modern DSLRs, but it’s a little more tricky than it was with film. In this video by Anders Lönnfeldt, photographer Christoffer Relander shows us how it’s done. Done well, it’s an amazing and fascinating technique. But, it is not one that’s easy to master.