In the Seasteading book, we quoted Erwin Strauss on this project:
Giorgio Rosa was (or is) a professor of engineering in Bologna, Italy. In the early 1960’s, he built a tower in the Adriatic Sea, in water less than 20 feet deep, about 8 miles off the coast of the Italian city of Rimini. This first tower was wrecked by a storm on February 13, 1965. A new one was built, with an area of about 4,000 square feet. It had a bar, a restaurant, a post office, a bank and a store, all surrounded by a promenade.