Of course, it would be best if we had a mountain or big hill to perform the ritual on, but Minnesota is sadly lacking in mountains. I would love to do the ritual on the river bluffs some year. In fact, I do believe its important to do ritual (when you can do it outside) near all four elements. We, ourselves, bring the fire and are the fire.
Having a standing stone or great old tree to stand in for the World Mountain and the World Tree is always good, especially if the stone or tree are near a well or wellspring, some source of water.
(sigh) Maybe, someday, I will have a nice bit of land and try and make sure there is a spring near a grand old tree. That would be just about perfect. Where I grew up, we had a spring and the water was wonderful. Cold cold in the summer and ice cold (almost too cold to drink) in the winter. We also had some oak trees and (behind the barn) black walnut trees.