Cambridge University Library is one of the most prestigious research facilities on the planet. It is one of only six legal deposit libraries in the British Isles, entitling the institution to a copy of every book, journal, printed map and piece of written music published in Britain or Ireland. This vast undertaking means that the library is constantly growing. The distinctive tower in the centre of the building is full of books so the library is now being extended underground. The library has a built in exhibition centre which visitors are welcome to visit and see some of Britain’s literary treasures.