When Marco Sanudo came to Naxos in 1207, he first captured the island's chief Byzantine castle, T' Apalirou. When Venice refused to grant Sanudo the independent status he desired, he broke away in 1210 and organized most of the archipelago into a Duchy of Naxos with himself, naturally, as the first Duke.

He built a powerful castle in Naxos Town (todays the Venetian Castle in Hora) which was consisting from 7 towers. Only two of the original seven towers (those of Sanudo and Glezos families) remain. The castle today includes a housing complex with the structure of a medieval city, one of the very few preserved in Greece. Venetians Catholic descendants still live in the old mansions which encircle the site.

In order make his fellows to stay in the island, he burned their ships. Sanoudos divided the island into territories and distributed them among his nobles. He and his successors, although ruling with a heavy hand, continued in power until the Turkish take-over in 1564, when the infamous Barbarossa conquered and plundered the island.