Gruta de Moinhos Velhos

The Gruta dos Moinhos Velhos, better than Grutas Mira Daire known, a cave complex in the town of Mira de Aire, in the central Portuguese district of Porto de Mos.

The show cave is the largest known cave in Portugal.

It was discovered in 1947 and is since 1955 under monument protection. To date, 8,000 meters are known.