Not only do I know why we are here behind these walls but I also know how the titans were made and were the walls came from because I'm the youngest granddaughter of the founder of our walled city.-
A lone time ago there was a man who lived far away from our little island that mans name was king Fritz he left his birth land to take refuge for his people the eldians.
He travels on a ship and landed on Paradis Island were he used a special power only true blood kings could use the power to shapshift into the very titans we fear. A song with his followers he used colasal titans and used there power to create the walls we live behind today.