地下道

• 土(earth; soil; land)RADICAL
• 也(also; punctuation mark (archaic))PHONETIC

The wide earth (soil) is also where all things flourish and grow.

• 一(horizontal line; boundary)RADICAL
• 卜(stroke descending downward)ASSOCIATIVE

A vertical stroke pointing downward across a boundary line marks 'below'.

• 辶(step; move)RADICAL
• 首(head; lead)PHONO-SEMANTIC

The head leads the way for feet to follow down a path.