The Biblioteca Nazionale Marciana is Venice’s national library, dedicated to preserving and showcasing the city’s manuscript and book heritage. It is one of the earliest public libraries in Italy and remains a major center for scholarly research on Venetian and classical texts.
It's a wonderful building. Designed by the architect Jacopo Sansovino. It is simple with just two orders. Ground floor: sturdy Corinthian columns with arches and sculpted heads. Upper floor: elegant Ionic columns with ornate capitals and decorative lion masks, reflecting Venice’s winged-lion symbol.
Cardinal Bessarion, a Greek Scholar and cardinal, donated his enormous personal library of Greek and Latin manuscripts to Venice in 1468, on the condition that it be kept public and accessible.
 
Interesting facts...
In the first room, you’ll find Fra Mauro’s World Map of 1450, one of the most fascinating pre-Columbian maps in existence. It shows the world before the discovery of America. Its also upside down!