The Ypsilon cave is a small but fascinating cavity on the lava of the Sciara del Follone (er. 1614/24). To reach it, you can orient yourself with the indicated coordinates or follow an old, little-known path, retraced and retraced by surveyors and called the Sentiero degli Sciatori “Direttissima” (for the Grotta del Gelo), which from Monte Timparossa led to the Grotta del Gelo, also included on the Open Street Maps, which in winter is inadvertently retraced by ski mountaineers to return from the famous cave to Piano Provenzana, passing by the top of the dagale di faggi on this side. This old mule track, cut by the 1947 lava in 2 points, is most likely the most direct and fastest, but also the most technical, path to reach the famous caves of the Lake, Aci and Gelo. The name of the cave is due to its shape that forks and resembles the Greek letter of the same name. Inside the cave, not very high, there are numerous remelting phenomena and the sandy bottom allows you to crawl through it. From a small hole in the vault at about midday a ray of light illuminates the cavity creating particular plays of light. Of remarkable beauty is the lava channel that is divided into several branches a little further downstream.