Tre Sassi fort (Italian Forte Tre Sassi or Forte Tra i Sassi; Ladino Fort Intra i Sas) is a fortress and museum on the road to the Passo di Valparola, within the comune of Cortina d'Ampezzo in the southern (Dolomitic) Alps of the Veneto region of Northern Italy. Hidden between the Ampezzo valley and the high Val Badia, it was built by Austrians between 1897 and 1901 as a fortification against attack from the Italians on the Falzàrego and Valparo. During World War I it was a favorite target for the Italians, and the fort was destroyed as there was inadequate artillery to defend it.