I am currently doing a university module on the history of the Venetian Republic - so hopefully I can answer this!

The History of Venice

There had been people living on the islands of the Venetian lagoon for some time, but it was really in the 6th and 7th centuries that migration to this area occurred. This involved people from northern Italy moving to the Venetian lagoon as it provided them with security from the barbarian invaders they were fleeing from; there was no Roman army to protect them any more. Initially, they settled on the most hospitable islands, which tended to be a bit higher and less marshy. As the population of the area grew, it became necessary to essentially engineer space. You have the correct idea with "columns", but to be more specific, those seeking to establish solid ground to build on cut down trees and drove them vertically into the ground as pilings, and topped these with horizontal planks, and later stone. Luckily, the conditions are perfect for these submerged trunks, and many of them today have endured since the start.

At this point, though, "Venice" didn't exist. The area was technically a territory under the jurisdiction of a Byzantine military official. The year 697 is the "official" Venetian date for the founding of the Republic, as this was the year in which the first Doge (from latin Dux, meaning Duke) was elected. Gradually, direct Byzantine influence in the area faded and so the transfer of power was fairly smooth. Nevertheless, Byzantium remained very important to Venetian trade for centuries. For a change in their relationship see the Fourth Crusade, in which Venice looted Constantinople.

Venetian power grew steadily over the centuries, as a result of several factors which include: geographical and political separation from the mainland and its politics; huge trade connections from its Adriatic base, which included exclusivity of trade in Byzantine ports, and an established link with the Levant; and its stable political system. Venice was extraordinarily wealthy, initially from its trade in salt, and later eastern goods e.g. silks and spices.

Venice established an overseas empire, the stato da mar, primarily in areas that were the most important in securing trade routes, e.g. Corfu (which secured the Adriatic; the Venetian mare nostrum). In the early 15th century, Venice began to expand onto the mainland in northern Italy, e.g. Padua, Brescia, Verona - known as the terraferma.

To truly understand the wealth and power of Venice, which is often overlooked in European studies in favour of the French/English/Spanish kingdoms, you can look at the war of the League of Cambrai in the early 16th century. This saw Venice undertaking a defensive war which is similar to something like Russia taking on the combined strength of NATO and several other nations, and surviving with fairly few setbacks. By the end of the war, Venice had regained the territory it had lost, and it did not take long for it to recover its strength. Venice was a major power.

This did not last forever. The expansion of the Ottoman sphere, especially into Greece, challenged Venetian trade dominance, and also threatened her militarily. Yet, Venice remained strong. This state of affairs persisted with little variation until the Republic was finally conquered, for the only time in its by-then 1100 year history, by the greatest military general since Alexander the Great - Napoleon.

So, to answer your question specifically. Yes, Venice is essentially a floating city supported by (wooden) columns. It came together primarily through necessity, as northern Italians desired the security offered by the lagoon. To say that this was a time of "limited technology" discredits the true ingenuity of those living in the period; to do what they did was clearly by no means beyond their technological capability. This seemingly impractical town grew to such a powerful city primarily because of its trade, which eventually reached a point at which it was self-sustaining.

If you have any other questions regarding Venice's empire, its trade or economy/industry, religious life, relationship with other Italian states, art, military/warfare, government, social order and institutions, then let me know.

For your purposes, the Wikipedia page for the Republic of Venice, whilst being somewhat brief and unorganised, is acceptable. If you find yourself wanting to read more into the topic, good general introductions include:

Longworth, Philip, The Rise and Fall of Venice, (London, 1974).

Ferraro, Joanne M., Venice. History of the Floating City, (New York, 2012).

Books by Thomas Madden have been popular, but I would avoid these, as he makes various claims which are not true throughout the book.