Dokodemo Door!

One of Doraemon's most commonly used gadgets is the dokodemo door, a door which allows travel to anywhere by simply going through the door. In an early story, the door is able to travel to the end of the universe, but in later chapters, the door is said to only be able to travel a maximum distance of 100,000 light years and cannot access other dimensions. Another limitation of the door is that it can only safely connect two known locations in its mapping computer, which also has a limited range of information based on Time