Crews squelching their way through sewer systems in cities around the world sometimes find that they’re not alone. Their headlamps and flashlights occasionally fall across fellow creatures—rats scampering through the filth, or bugs, or even amorous amphibians. Some Victorian-era Londoners circulated stories about feral swine thriving down in the damp, and New York City residents have been talking about subterranean alligators for more than a century. In mid-November 2020, crews working on a sewer project in Athens stumbled across a notably different figure. It wasn’t something slithering or scuttling, but…
