Landforms and water
Long Mai (dragon vein)
The current of qi running down along a mountain ridge.

The form school likens ridges to dragons: a spur branching off a great mountain and winding down is the dragon vein. A ridge that meanders gently is read as alive, one that drives straight down as harsh. Where the vein halts and qi knots is the point (Xue) — which is why the form school's order of work is to read the dragon, then find the point.
Related landforms
Source: Standard form-school feng shui (Xingqi) — the landform tradition