I would strongly advise against entering such tunnels. Besides being highly illegal, as I already said, it is very dangerous.
I would tell anyone interested to check out the website, Handbook of Texas online.They are right now revising their website.But you can type in google search Southton,Texas and maybe the old page from the Handbookonline will pop up and you can read about the place.Also www.texasescapes.com has information on the community of Southton,but not sure if it mentions this asylum. Also the Cyndy Taylor Krier Juvi place is named for a local lady judge. For you folks living in San Antonio and the surrounding area, watch WOAI,Channel 4, Cable channel 3, at 10:00 tonight.
One of their reporters spent the night at Victoria's Black Swan Inn in San Antonio on Holbrook Road,near Fort Sam Houston.The house was built in 1867 on the site of the Battle of Salado and is haunted.The Psychic Peter James visited the place for the show,Sightings if I recall correctly.