On the table in the light of a big lamp with a
red shade he spread a piece of parchment
rather like a map.
“This was made by Thror, your grandfather,
Thorin,” he said in answer to the dwarves’
excited questions. “It is a plan of the Mountain.”
“I don’t see that this will help us much,” said
Thorin disappointedly after a glance. “I
remember the Mountain well enough and the
lands about it. And I know where Mirkwood is,
and the Withered Heath where the great
dragons bred.”
“There is a dragon marked in red on the
Mountain,” said Balin, “but it will be easy
enough to find him without that, if ever we arrive
there.”
“There is one point that you haven’t
noticed,” said the wizard, “and that is the secret
entrance. You see that rune on the West side,
and the hand pointing to it from the other runes?

That marks a hidden passage to the Lower
Halls.” (Look at the map at the beginning of this
book, and you will see there the runes.)
“It may have been secret once,” said Thorin,
“but how do we know that it is secret any
longer? Old Smaug has lived there long enough
now to find out anything there is to know about
those caves.”
“He may—but he can’t have used it for
years and years.”
“Why?”
“Because it is too small. ‘Five feet high the
door and three may walk abreast’ say the
runes, but Smaug could not creep into a hole
that size, not even when he was a young
dragon, certainly not after devouring so many of
the dwarves and men of Dale.”

The Hobbit, Chapter 1: An Unexpected Journey