One of Giannutri's biggest draw cards is its incredible wealth of Roman ruins. In many cases, they are better maintained here on the island with the wind and the sea than on the rest of mainland Maremma Tuscany.
The island's Roman ruins surround Cala Maestra, a beautiful bay to the north-west. If you wander a little bit into the brush, you'll find the remains of a Roman villa that dates back to the 1st century BC.
The villa was built by the ancient senatorial family of Domizio Enobarbo, whose head was Gnaeus Domitius, husband of Agrippina, mother of the Emperor Nero. Part of the villa was renovated to accommodate a more modern resident in the 19th century, but much of it was left untouched.
In Cala Maestra, head down to the waters and you'll see the dock that once opened into the Roman port. A beautiful find, it's not really protected by anything and you can really get up close and admire it.
The pillars stand like stalwarts looking out to sea. They're made from a local marble that has withstood the elements without what appears to be an ounce of difficulty.
On an aside, the water at this beach is also nice for a swim, if you've got some free time.
In Cala Spalmatoio are some more Roman ruins from the old port, while on your way to the villa, you'll find everything from public baths to cisterns that are still used today.
The Romans lived and built a mini empire on this island, but the best way to explore this patrimony is to hire a guide. A lot of Giannutri Island is closed to visitors, so if you're keen, get a guide.
You can find a list of accredited guides on the island's parks website.
For more info about the villa: check out the official Parco degli Etruschi government website.