Currently (2015), there are three cities in Mexico with an underground rapid transit system:
Naica, on the state of Chihuahua.
Carlsbad Caverns.
the Yucatan Peninsula
New Mexico
Carlsbad Caverns.
The Underground Railroad lead to Mexico, New York, even Canada. It led to Canada because Canada did not allow slavery
Carlsbad caverns
Plane Car Jump the border Swim Rio Grande Make underground tunnel
it was taken place in mexico the carribean and some of new orleans
Natural Gas
I believe you are looking for the Ogallala Aquifer.
The nearest body of water from Monterrey Mexico is Santa Catarina River. This river is actually an underground river which appears at the surface during the rainy season.