The rabbit burrowed underground.
It was a bit too dark underground for Bob's liking.
The underground base was compromised.
A spirit raised from depth of underground.
I am between stations of the Underground Railway.
The Underground railroad helped many slaves to freedom.
The Chileans were stuck in a mine *underground* for almost 2 whole months.
The water table is underground. Mining is used to extract ores from underground. The placement of underground utility wires must be marked.
Example sentence - The underground passageways were wet, dirty, and scary.
Example sentence - The underground blast caused the mine to close.
The Underground Railroad was a network of secret routes and safe houses used by slaves to escape to free states or Canada.
Cuniculus is an underground drain that runs through the city. This is an example sentence for cuniculus.
Groundwater is always underground!
Yes I have reason to believe that its capitilized
I walked through the underground labyrinth and got lost.