Unseen University was much bigger on the inside. Thousands of years as the leading establishment of practical magic in a world where dimensions were largely a matter of chance in any case had left it bulging in places where it shouldn't have places. There were rooms containing rooms which, if you entered them, turned out to contain the room you'd started with, which can be a problem if you are in a conga line.

The Last Continent: (Discworld Novel 22) (ed. Random House, 2008) - ISBN: 9781407035123