Outer Space is what Fraggles call the world outside of Fraggle Rock where the Silly Creatures live. Therefore, whereas Doc's Workshop is considered to be part of Outer Space, the Gorgs' Garden is not.
Traveling Matt discovered the once-fabled Outer Space in the first episode of Fraggle Rock, "Beginnings," and has since spent much time exploring it. He regularly sends postcards detailing his adventures to his nephew Gobo.
Matt misinterprets everything he sees in Outer Space. For example, in the episode The Garden Plot, Traveling Matt believes people roller blading and skateboarding are Silly Creatures who have evolved wheels on their feet. He sometimes believes that creatures that live in Fraggle Rock, like Gorgs for instance, also live in Outer Space.
Traveling Matt also often visits famous sights, such as Buckingham Palace. He also visits normal, everyday locations like subways and schools. He still, however, misinterprets everything.