Monumento naturale Grotte di Falvaterra e Rio Obaco, Natural monument and karst cave system in Falvaterra, Italy.

Monumento naturale Grotte di Falvaterra e Rio Obaco is an extensive underground cave network beneath Monte Lamia containing flowing streams, cascades, and pools of water. The passages display white limestone formations and extend for several kilometers underground.

The cave system formed through geological processes over vast timescales and shows traces of early human presence through ancient polygonal walls. These structures indicate settlement activity in the area since pre-Roman times.

The site's name comes from the Falvaterra caves and the Rio Obaco stream that resurges from them. Since March 2013 a unicursal labyrinth of rocks, mosses, stones and plants, designed by researcher Giancarlo Pavat and commissioned by Prof. Augusto Carè, stands near the visitor centre. The caves receive about 10,000 visits a year.

The first 250 metres of the tourist route are accessible to wheelchair users and are walked on metal gangways; the river below can flood with several cubic metres per second, producing loud cascades and rapids. Canyoning and speleotourism in the inner sections run mainly from May to September, with guided trips of over 1,000 speleologists a year; autumn and winter visits depend on weather checks.

The caves contain formations called pseudo-siphons and connect to the neighboring Pastena cave system through an underground passage. This hidden link reveals the vast scale of cave networks lying beneath the mountains.