Which level of security is highest in the federal prison system?

The highest level of security in the federal prison system is the "Supermax" facility, specifically the ADX Florence in Colorado. This prison is designed to house inmates deemed the most dangerous, including those convicted of terrorism and violent crimes. Inmates at Supermax are held in solitary confinement for 23 hours a day and have very limited contact with the outside world, making it one of the most secure environments in the U.S. penal system.