The baroque library was first opened in 1722 as a part of the Jesuit university based in Klementinum. It houses over 20,000 volumes of mostly foreign theological literature, coming into Klementinum from the beginning of the 17th century until recent times. Books with white painted spines and red marks have been in the library since the time of the Jesuits.
The interioir of the baroque library has remained intact since the 18th century. The hall is decorated with ceiling frescoes by Jan Hiebl depicting allegorical motifs of education, and portraits of Jesuit saints, patrons of the university and prominent representatives of this order. At the head of the hall is a portrait of Emperor Joseph II., who arranged for the books from abolished monastic libraries to be sent to Klementinum. Also remarkable is the collection of geografical and astronomical globes in the center of the library. These are mainly works of the Jesuits. Among the globes are also astronomical clocks, constructed mainly by Jan Klein.
In 1777, the library was declared by Maria Theresa as Public and University Library. In 1781, its director Karel Rafael Ungar established a collection of literature written in Czech language called Biblioteca Nationalis, thereby giving the basis for a national library. This collection is now under the same name located in the head of the hall at the gallery.
The library currently contains a number of important and unique works, that have global significance.
Also worth mentioning is the fact that the National Library has recently provided some historical books to Google for digitization. After the completion of the entire process the books will be available in a digital library on Google Books.