The Great Lock-up

Alcatraz housed for 29 years the worst of the worst prisoners. The purpose of prisons is to punish the offender and to keep dangerous criminals off the streets. Satan is Public Enemy #1 and we see in this passage of Revelation his fate and punishment. He will be bound for 1000 years. But there are questions:

1. What are the inmates?
2. Where is the prison?
3. What is the purpose of the sentence?