Tucked into the Szinva Valley at Lillafüred, Szent István Cave is one of Hungary's most spectacular show caves — a glittering underground world of stalactites, stalagmites, frozen waterfalls and towering columns that have amazed visitors since the cave opened to the public in 1931. What makes it truly special is the combination of extraordinary formations and remarkably pure air: the cave's atmosphere is completely pollen-free with nearly 100% humidity, making it not just a tourist attraction but also a certified healing cave.

Carved through Triassic limestone at 331 metres above sea level, the cave stretches for 711 metres and forms the lowest link in a vast underground system beneath the Létrás plateau. Its passages tell a dramatic story — water flooded the cave in both 1958 and 1974, bursting out onto the roadside. Today, atmospheric LED lighting illuminates highlights like the 'Mamutfogsor' (Mammoth Tusk), the fairy-tale 'Meseország' (Fairyland) section, the majestic 'Oszlopok csarnoka' (Hall of Columns) and the dramatic 'Színházterem' (Theatre Hall). The deepest point, known as 'Pokol' (Hell), is flooded year-round and marks the limit of exploration.

• Lillafüred (parking near the Palace Hotel) — cave entrance is right alongside the Lillafüred–Eger road, short walk, easy

• Open to tourists since 1931; guided tours only
• The 'Black Hall' has functioned as a therapeutic cave for children with respiratory conditions since 1988; declared a healing cave in 1991
• Strictly protected natural monument within Bükk National Park; non-public sections require a permit from the park directorate
• A new entrance building was completed in 2001

According to local legend, the cave was discovered in 1913 when a dog fell through the natural opening — a 15-metre-deep shaft — and its whimpering led explorers to the entrance, earning the cave its old nickname 'Kutya-barlang' (Dog Cave).