Vastness is a huge void that contains The Rock. It is completely empty, with absolutely no life. It would already be ridiculous that you even got here, since it lies beyond even infinite fractals and huge cosmic structures.
The temperature here is so cold, it is colder than "infinitely cold". The temperature in Vastness is just called "Coldest". If you somehow manage to escape The Vastness, you will end up in The Great Big.