Editor' note: World Book Day, also known as World Book and Copyright Day, is an annual event organized by the UNESCO to promote reading, publishing and copyright. The first World Book Day was celebrated on April 23 in 1995. As this year's day for knowledge is coming, let's take a look at the world's fascinating libraries and enjoy the fun of reading.

1. Royal Portuguese Cabinet of Reading

Located in the center of Rio de Janeiro, Brazil, the Royal Portuguese Cabinet of Reading is a library and cultural institution. It was built in the late 19th century under the stewardship of an association of Portuguese migrants.

Open to the public since 1900, the cabinet has the largest collection of Portuguese literature outside Portugal, holding more than 350,000 books.