Where in Texas is there a “subway line”?
There used to be a small privately owned subway in Fort Worth. I’m a native of Texas but I found that on Google.
The Cityplace rail station is over 120 feet underground.
See some station photos here:
The north end of the subway tunnel ends in an open cut at the Mockingbird station, a couple of miles north, and about 3 stories below ground level. See a view down into the Mockingbird station here http://en.wikipedia.org/wiki/Mockingbird_Station with the tunnel entrance visible
An intermediate station at Knox has been dug, but was not finished out due to neighborhood objections. The south end of the tunnel is in downtown Dallas. The tunnel itself is between 3 and 4 miles long.