Based on latest evidence and calculations, our entire galaxy, the Milky Way, might be a a huge wormhole, stable and navigable. Astrophysicists combined the equations from general relativity with a distribution of dark matter to reach this conclusion.
A wormhole is a hypothetical feature that is fundamentally a shortcut through spacetime. A wormhole is much like a tunnel with two ends, each with very different locations in spacetime. Read more about Our Galaxy Could Be One Big Universal Travel Tunnel