1.) Library of Congress-Washington D.C.
If there was ever a dream job, mine would be here. The Library of Congress was built for the United States Congress in 1800 and today it is the research library for members of Congress as well as being the de facto national library of the United States. It's also the largest library in the world by shelf space and number of books, which is quite impressive considering how many libraries exist. Although only members of Congress, Supreme Court justices, and other high-ranking government officials can check out books, I'd still visit just to tour the buildings. (There are a total of three-the Jefferson Building, the James Madison Memorial Building, and the John Adams Building.) All feature Italian marble floors inlaid with brass and concentric medallions as well as countless murals, paintings, and other priceless treasures. Its holdings are also quite impressive-a rough draft of the Declaration of Independence, a Gutenberg Bible, the Betts Stradivarius (an antique violin made in the early 18th century) and one million issues of world newspapers from the past three centuries.
In the library world, this is one of the most revered buildings from an architectural standpoint. Opened to the public in 2004, the 11-story building is made of glass and steel and consists of several "floating platforms" wrapped in a large steel net around glass skin. Inside, a major section of the library is the "Books Spiral" which was designed to display the library's nonfiction catalog without breaking up the Dewey Decimal classification onto different floors or sections. The collection spirals up through four stories on a continuous series of shelves. Not your typical brick and mortar library.
Trinity College was the first place we visited after arriving in Ireland and due to extreme fatigue from jet lag, it's a place I'd like to see again, when I'm well-rested of course. Trinity is home to the famous Book of Kells, an illuminated manuscript in Latin, containing the four Gospels of the New Testament and created by Celtic monks around 800. I greatly enjoyed walking the halls of the Long Room, the main chamber of the Old Library which houses 200,000 of the library's oldest books. It was a wondrous sight for the eyes, or for an ardent bibliophile.
Although the Royal Library of Alexandria long since ceased its operations (historians and archeologists estimate that the library was destroyed more than a thousand years ago), in the ancient world, it was the largest and most significant great library. It is said to have flourished under the Ptolemaic Dynasty and functioned as a major center of scholarship from its construction in the 3rd century BC until the Roman Conquest of Egypt in 30 BC. It was the first known library of its kind to gather an extensive collection of books from beyond its country's borders; it was given the task of collecting all the world's knowledge. The Bibliotecha Alexandrina was built as both a commemoration and emulation of the original Royal Library of Alexandria in 2002, near the site of the old library.
The Library of Celsus was built in honor of the Roman Senator Tiberius Julius Celsus Polemaenus in 135 AD by his son, who paid for the construction with his own money. It was built in what was traditionally Greek territory, so it is one of the few remaining examples of a Roman-influenced library. It was built to store 12,000 scrolls and to serve as a monumental tomb for Celus, who is buried in a sarcophagus beneath the library.