Underground is a 1995 movie by Emir Kusturica dramatizing not only an heterotopia but also an heterochronia. In fact, the topia here is a underground resistant shelter in Yougoslavia started during the Second World War. The heterochronia is constituted by the fact that, many years after the end of the war, this little node of resistance continues to organized itself in order to resist to nazis. Their only contact with the surface world being a manipulator/opportunist general, people living in this underground world have no idea of what is going on outside their universe which insists here on the filtration of exchanges between an heterotopia and the normative world.
Thanks for the reminder Camille.