This is truly one of the most fucked up things I have ever heard. The Julia Tuttle Causeway is a strip of highway in Miami-Dade, Florida that houses approximately 140 sex offenders. They live in a communal shantytown below the highway. Why? Because there is a housing crisis for sex offenders in Miami.
Miami-Dade County laws state that convicted sex offenders cannot live 2500 feet (roughly 1/2 mile) from any school, child care facility or playground. That is the strictest such law in the country. They can't even live near a homeless shelter because of the children that live there. So the colony was created below the Causeway because they have nowhere else to stay. Currently, when a sex offender is release from a Miami-Dade jail, they print a default address of the causeway on it. Some of them have generators, camping showers, pets and makeshift plumbing. They live in tents or cardboard box constructions.
What is even more disturbing is that the law seems to be backfiring. It only requires them to be at their residence from 6pm to 7am each day so some of them actually go to their old homes each day to shower, cook, eat, watch TV with the family, use the net etc. If the law was less restrictive, they could actually get an apartment and carry on a more normal life. Obviously, these folks have some serious problems to deal with. Further isolating them into their own ghetto seems more likely to alienate them than to help them assimilate.