The Greek island of Keros surely impressed ancient visitors, with terraces and buildings made of gleaming white stone jutting out of the Aegean Sea. As it turns out, what couldn't be seen may have been even more impressive, reports the Guardian. An international team has uncovered a sophisticated plumbing network that predates similar networks at ancient sites by some 1,000 years, reports National Geographic. Scientists, who are trying to determine whether the drainage system carried freshwater or sewage, also discovered two workshops—inside of which sat a clay oven, lead axe, copper dagger mold, and copper-coated ceramic pieces—likely used by "proficient metalworkers," according to a press release.
"We probably are dealing with a kind of expertise that was not widely shared," says excavation co-director Michael Boyd. "It just gives this impression of [Keros] being a very cosmopolitan and international place." This is especially impressive as everything from stone to metal ore to most food had to be imported. Indeed, archaeologists believe 1,000 tons of white stone covering the Dhaskalio promontory—which was connected to the island at the time by a causeway now underwater—came from the island of Naxos, six miles away. Excavations resume at the site in September. (The oldest known erotic graffiti was found on this Aegean island.)