The Baroque Library is the best example of Portuguese Baroque and is considered to be one of the richest European libraries. It is also known as the Joanina Library in honour and memory of King John V, who authorised its construction and whose portrait, painted by Domenico Duprà, distinctly dominates the space inside the Noble Floor. 

Construction on the Baroque Library was completed in 1728.  It functioned as the University Library from 1777 until the first half of the 20th century.

It holds 60 thousand books, dating from the 16th century to the 18th century, on a wide variety of topics that can still be consulted today.

This building is devided into 3 floors:

 The Noble Floor

The Noble Floor consists of three halls filled with shelves and varandas ornamented with rich carvings and gold paintings against a black background in the first hall, a red background in the second hall and a green background in the third hall. The three halls are connected by archways decorated with crests. The lining is made of wood, painted to resemble marble. The walls are lined with two storeys of gilded multi-coloured oak shelves. Six embossed tables made from precious tropical woods can be found throughout the halls. The figures on the ceilings were carefully chosen and contain messages connecgted to the University's ideals that are still relevant today.

The three floors that make up the building house nearly 60 000 volumes, representing the best of what was printed throughout Europe between the 15th and 18th centuries. Most of these books are part of our electronic catalogue and are still sought after. An average of 750 works are requested each year. The Library is undertaking a selective digitalisation process.

The building is a vault primarily designed to preserve books: the exterior walls are 2 metres 11 centimetres (6 feet, 11inches) thick. In addition to moisture and temperature, books can also be affected by insects that feed on paper. To prevent this, the shelves are made from oak, known for their density, durability, and odour that keeps insects away.

For about two and a half centuries, two colonies of bats have lived in the library to help with pest control. The presence of these mammals, however, requires additional precaution: at the end of each day, the tables are covered with leather "towels." This procedure, which was common in temples and palaces, still helps to prevent the damage caused by the animals' waste products.

The Middle Floor

This hall served two purposes: it supported the guards who watched over the academic prison (closed in 1834) and operated as a deposit for the books read on the Noble Floor.

Prior to its inclusion in the University's tourist route (on 1 November 2010), this space was used for the preservation of ancient books: cleaning, restoration, and cataloguing.

It is thought that during the 19th century, the floor may have also have been used as living quarters for professors and other members of the academic community.

Initially, there was no easy access between the intermediate floor and the noble floor. The stairs that today connect the two floors of the Library were only built at the end of the 19th century. The floor is still used for the exhibition of documents.

One of the most interesting elements about this space are the small markings on the stones of the arch, made by the stonemasons, which are still visible today. In essence, little care was taken to create a rich and beautiful space on this floor. The finishings are simple and the stones were kept in their natural state. Each stonemason had his own "signature," which made it easier for each one to account for the work completed in order to receive their payment.

The Prison

Similar to other prestigious European universities, the University of Coimbra for a long time had the privilege of governing itself and had its own legislation (Academic Forum). This privilege protected the academic community (professors, personnel and students) from living with common criminals. This was the case until 1834, when the privilege was revoked.

After having been located in other places, the academic prison also operated here, more or less coinciding with what had formerly been the Royal Palace prison.

What we see is a prison of medieval origin, the oldest one that has been preserved in Portugal. Two narrow cells and a winding staircase remain of the primitive structure.

In 1782, following the university reforms carried out by the Marquis of Pombal, the space underwent several transformations: communal cells, a visiting room, a prayer room, and even latrines were added, all of which are visible from the more spacious room.

More recently, the ground floor operated as a book deposit. This happened during the period following the extinction of the university colleges, most of which were located in the lower part of the city. In some cases, the libraries that served those colleges were transferred here and to the intermediate floor, remaining there for several years, waiting to be catalogued and placed in the upper floors of the library.