The Biblioteca Joanina is one of the world's most magnificent Baroque libraries, built by King João V in the 18th century. It houses over 300,000 rare books dating from the 16th century. The interior dazzles with gilded carvings, painted ceilings, and ornate wooden bookshelves. The library is famous for its colony of bats that protect the books from insects at night. As part of the UNESCO-listed University of Coimbra, it represents the pinnacle of Portuguese architecture and knowledge heritage. Tickets must be booked in advance as visitor numbers are strictly limited to preserve the delicate interior environment.