The infinite vastness of space.

That could work by wrapping our three dimensional space around a fourth dimension, no?

No...

Wouldn't that only work in a closed universe?

It's somewhat paradoxical, but I really don't think that the universe has infinite matter. The only reason that the universe can be considered infinitely vast is that its true size is not truly known. However, even though the true size is unknown, people can still define an infinite volume to contain the universe. The infinite volume is what I'm going at.

It's like how radial coordinates wrap around origin infinitely many times, even though people often choose to stop drawing graphs at 2π.