In the 15th century Porto Ercole was bought by the powerful Republic of Siena, who fortified and enriched the town. But Siena was allied with the French, and when the equally powerful Duchy of Florence formed an alliance with Spain and they all started fighting over Italy, an important battle took place in Porto Ercole, the Spanish won, built a bunch of forts and enlarged the port, and the town entered it’s most prosperous period.

Caravaggio died here in 1610, exiled by the pope from Naples, landing on the beach at Feneglia in a small fishing vessel, already deathly sick, hiding from the authorities in the woodland there, and eventually given refuge in the Church of Saint Erasmus in town. And Porto Ercole was also a summer vacation home of the Dutch royal family for more than fifty years in the 20th century, so much so that Queen Juliana retired here after she abdicated the throne in 1980.