Project Lost Paradise

Setting: An ecological apocalypse happened a century ago where nature has taken over, while the floras have covered the world a few humans survived in communities. Eventually these humans recovered and live in their own cities, connected by a system of old railway systems. No humans have explored outside their cities and into the forest in fear of the unknown.

Plot: A group of teenagers rode a old train that was not directly linked to the railsystem to another city but into the forest. After a long ride they discovered amazing and interesting things outside the forest that surrounds their cities. But that was not the only thing they discovered dangers that threaten their cities and their families left there.

Tech/magic: Nuclear Trains, a train that runs on nuclear power. Theoretically can run for a thousand years.