At monstown, unnatural selection you can create and take care of monsters at the Ranch, battle other monsters on the Stadium and unlock stuff at the Museum.
Ranch - There are 8 available ranches that can be unlocked. Each one you can build facilities that produce food, create monsters and evolve them.
Stadium - Here there are 45 levels where you can challenge the enemies to win "Evolve Points" (EP can be used to evolve monsters at the ranch).
Museum - Here you can check what to unlock.