Hollgrotten

Most caves are dissolved out of rock over hundreds of thousands of years; the Hollgrotten are the opposite - they are built up. Calcium-rich water from the Lorze precipitated tufa around moss and vegetation, forming chambers, drapes and columns in a period usually given as a few thousand years, which is very fast for cave formation. Quarrymen cutting tufa for building stone broke into them in 1863 and they opened to visitors soon after; the lighting scheme, largely unchanged in style since the early electric era, is part of the character. The gorge outside is a pleasant walk from Baar with mills and a river path. The formations are fragile and touching them is not allowed.

What you actually see

• Caves that were built, not dissolved - tufa deposited around vegetation.
• Formation in a few thousand years - very fast by cave standards.
• A quarry discovery of 1863 - found by men cutting building stone.
• Period lighting - an old-fashioned scheme kept as part of the visit.

When to go

April to October. Two hours with the gorge walk.

Honest expectations

Closed all winter. The route is short - under half an hour inside. It is damp and the steps are slick. Formations are fragile, so the path is railed and photography is awkward.

Nearby

Baar and the Lorze gorge path are alongside; Zug is south-west.