Great Library - The greatest repository of writing in antiquity, the Library of Alexandria was not necessarily designed for that purpose. It was intended, first and foremost, to demonstrate the glory of Alexandria, and the glory of Egypt. The fact that it acquired knowledge from throughout the known world and brought it to a single location was an added benefit. Built in the time of Ptolemy II Philadelphus (283-246 B.C.), the library was part of a larger complex called the "Musaeum". Ptolemy II truly had one of the most glorious reigns in history. Besides the library, the Lighthouse of Alexandria (above) was also built under his auspices. The Musaeum, which means "temple of the Muses", was a school, not a museum in the modern sense of the word. It was modeled after Aristotle's Lyceum, which was no accident because the complex was organized by one of his students, Demetrius of Phaleron.
The scholars (and Ptolemy himself) were so determined to collect every piece of writing known to man, that they had an acquisitions department whose job it was to find and bring them to the library. Even to the point of confiscation. One example is, according to the physician Galen, that any book found on a ship entering the city, was taken to the library and copied. The original was kept and the copy given back to the owner. In an even more egregious example, Ptolemy III (Ptolemy II's son) asked Athens if he could borrow the original works of the three great tragedians (see Aeschylus, Sophocles and Euripides). By this time they were nearly two centuries old. Athens agreed in exchange for an enormous deposit of gold, about 15 talents. Ptolemy paid, and then simply added them to the library. It's impossible to know how many scrolls it contained at its height, but it's estimated to be as many as 500,000. The Library of Alexandria can be likened to today's Library of Congress in Washington D.C., which collects every published work in the United States (but may not keep them permanently). One of the most famous legacies of the library, begun under Ptolemy II, was the translation of the Hebrew Bible into Greek, known as the Septuagint (see LXX above). The library, and the larger Musaeum as a whole, as well as other learning institutions, such as Euclid's school, made Alexandria one of the intellectual centers of the world in ancient times. Sadly, it was burned, accidentally, by Julius Caesar's troops in 48 B.C., after they occupied the city while trying to catch up to Pompey during the Roman Civil War. It's not believed the works were entirely lost in the fire, but the destruction of their sanctuary doomed the survival of those that were saved in the centuries that followed. The loss of such a vast collection of ancient writings is perhaps the greatest misfortune in history. Just imagine how much more knowledge we would have of the ancient world had they survived.