Laniakea

This story takes place in the future, when superluminal speeds allow for travel to any point in the universe. People are hoping to find extraterrestrial life, but as of yet no one has succeeding in finding anything. One day, a lonely man finds a message in a monolith that has been drifting in space. It helps him to find a portal that leads to the home planet of those who made the monolith. He finds a giant structure, a building. But ...This place is breathing on its own. Where has everyone gone?