There was, indeed, light at the end of the staircase. And outside space. He had to shield his eyes for a moment after opening the door and walking out, he had gotten used to the darkness of the tunnel. Once he could safely open them again though, he finally got a chance to look around.
He'd stepped out of a small wooden shed, what looked like one at least. Inside it was only the staircase he'd used to get there, though he did wonder if things would stay the same once he closed the door. Or if the shed would still be there at all once he left. Somewhat out of curiosity, he closed the wooden door, and found he could not open it again.
Satisfied, he turned and had a look at the rest of his surroundings. He saw a few trees and hints of a hill in the direction he'd come from, and houses on the opposite side, separated from him mostly by grassy fields. And among those houses a taller structure stood out from the rest, gleaming in the sunlight and looking somewhat like a tree.
The stallion quirked an eyebrow, then pulled out a book from his saddlebags and pulled out a picture from the book. Looking between the two, it was undeniable that the castle he was seeing in the distance was the same one in the picture. Which made sense. Having gotten there so quickly was the part that didn't really make as much sense, considering he'd only travelled for less than a couple of days, but he wasn't about to complain.
He placed the picture back into the book, put the book back inside his saddlebags, and then began to walk towards Ponyville and towards the crystal castle in the middle of it.