Astroni is one of the wonders of the Campi Flegrei: an entire volcanic crater carpeted with Mediterranean vegetation. Tapped by the Romans for its geothermal waters (the baths have never been discovered) and used by Naples' various dynasties as a hunting area from the 15th to 19th centuries, Astroni is now a World Wildlife Fund (WWF) reserve. A landslide after heavy rains in March 2005 blocked the road (near the site entrance) that winds down towards the lakes on the crater floor; visitors have since been channelled down a steeper path through holm oak woodland.
A shady picnic site has been laid out at the crater bottom, and screened observation walkways have been erected for birders by
the lakeside, but much of the area is so dense in vegetation that birdwatching here requires a good pair of ears as well as binoculars. Although it sounds idyllic, be warned: access by public transport involves a two-kilometre walk through an isolated area and opening hours are subject to change, so phone ahead.