The city of Venice stretches across 118 small islands in the saltwater Venetian Lagoon, between the mouths of the Po and Piave rivers. No exact date is known for the founding of Venice, but some archeological evidence shows that the city's original citizens may have been Roman refugees fleeing the Germanic invasions and the Huns. As the centuries passed, the originally small settlement began to spread across the islands, its inhabitants using the small rivulets and canals as their roads. The city fell under Byzantine rule early in its life. In the late 700's AD the ducal seat was moved to Venice and a basilica dedicated to St. Mark the Evangelist was built, heralding the birth of the "Queen of the Adriatic". The city eventually gained its independence from the Byzantines and became an autonomous city-state.
The city flourished as a trade center between Western Europe and the rest of the world, its strategic location making its commercial and naval power unmatched in the Adriatic. Venice began to expand outside of the islands as it seized cities along the eastern shores of the sea, later extending its holdings as far west as the Adda River in mainland Italy. It soon came to control most of the islands in the Aegean Sea, including Cyprus and Crete, and became a major power in the Near East. While it did take most of these cities and regions by force, the people of its empire quickly rallied to Venice's aid whenever she was threatened by invaders, as the city-state actively improved the standards of living in all these territories.
Venice's dominance was further secured in 1204 when it sacked the city of Constantinople, securing the fall of the Byzantine Empire. Considerable wealth was brought back to the city, and combined with its already formidable riches from trade, made Venice the wealthiest city in all of Europe. The city also became known as a hub for culture, music, and the arts, and was especially famous for its operatic composers. Venice can also lay claim to the invention of the paperback book, and by 1492 was the printing capital of the world.
The glory days for Venice couldn't last, and a war with the Ottoman Empire cost the city most of its eastern Mediterranean holdings, including Constantinople. Shortly thereafter Christopher Columbus discovered the New World and Portugal found a sea route to India, peacefully destroying Venice's trade route monopoly where all others had failed. In the late 1500's the city was ravaged by the Black Death, which killed over 50,000 people in three short years, a third of its total population.
On May 12, 1797, Napoleon conquered Venice and ended over 1,000 years of the Republic's independence. Venice then became the property of Austria when Napoleon signed it over later that year. A revolt in the 1800's attempted to restore independence to the Republic of Venice, but in 1866 it became a part of the newly created Kingdom of Italy.
The current threat to the city comes not from war or encroachment upon its trade economy, but rather from the very environment around it - the city has slowly been sinking into the sea since artesian wells were dug into the lagoon bed in the early 20th century. The sinking has slowed dramatically as measures are being taken to preserve the city, but new plans are being put in place to either build an inflatable bulkhead (to stop rising tidal waters) or to physically raise the city itself by restoring the seabed damaged by the wells.