When the Silver Surfer was sent to the Macroverse by Tenebrae he was awed by the thought of so much new discovery. It contains innumerable worlds and wonders.
 
He met a resident of the universe, Sama-D, who explained that the Macroverse is really the Surfer's universe but with quite a few others. 
 
At the furthest edges of the Macroverse is what is referred to as 'the door'. It is where the Macroverse simply ends. To enter this termination means to be utterly annihilated and no longer exist. The Surfer was able to succeed after his second try.