This is a prison in central La Paz. Apparently, it's a guard-less prison. Basically, if you break the law, you get stuck in here. But it's just like the outside world - with shops, restaurants, cocaine labs inside - you just can't get out of it. I understand that the reason most backpackers go to La Paz is to try to get in to see - it's kind of become a sport. Everyone you meet has a story about how they were so close to getting in. It's all because they read this book Maching Powder. I, personally, had no interest in any of it.