Learn Dutch: Het pad loopt om de grote rots heen. - The path goes around the large rock.

This is a circumposition, a two-part preposition used to emphasize a path or direction. While om by itself can mean 'around', adding heen after the noun (de grote rots) specifically highlights the continuous route going all the way around the rock.

Why does the sentence use loopt when a path cannot walk?

Although lopen literally translates to 'to walk' or 'to run', Dutch naturally uses it to describe the physical route of stationary things that span a distance. You will often see rivers, roads, pipelines, and paths 'walking' (lopen) where English would use 'going', 'running', or 'leading'.

What determines exactly where heen is placed in the sentence?

In a circumposition like om ... heen, the two parts bracket the object they refer to. The first part (om) goes before the object, and the second part (heen) goes immediately after the complete noun phrase that the path wraps around, which in this case is de grote rots.