San Antonio is a city in Texas.
In the Empowered universe, San Antonio was the location of a large capeless uprising against superheroes and supervillains that occurred five years before the start of the main story and which has had lasting consequences in the caped community.
In The What-the-Fuckiest Five Minutes of My Career So Far, the television program Super Dirty Jobs shows that San Antonio is now the site of a supervolcano.
In I Never Looked in Your Eyes; I Never Heard Your Voice, it is revealed that the supervolcano was created by the Vorpal Sword superweapon, which went out of control after being deployed by the capes and bored a hole through the planet's crust.