Geysir Andernach

A borehole drilled in the early twentieth century on a peninsula in the Rhine tapped groundwater saturated with volcanic carbon dioxide. The gas comes out of solution as pressure drops in the pipe, the column lightens, and the whole thing erupts, throwing water up to around sixty metres; because it is driven by gas rather than heat, the water is cold, and it is the tallest cold-water geyser known. Eruptions occur roughly every ninety minutes to two hours and last about eight minutes. The site is reached only by boat, timed so visitors arrive for an eruption, with a museum on the mechanism at the landing.

What you actually see

• The cold eruption - a column up to about sixty metres driven by gas.
• The timed boat - access by boat scheduled around eruption times.
• The museum - displays on the geyser's mechanism and Eifel volcanism.
• The peninsula - a Rhine island reserve with the borehole at its centre.

When to go

April to October; the site closes for winter, roughly November to March. Boats run to a schedule tied to eruption times and must be booked in season.

Honest expectations

It closes for several winter months and access is only by ticketed boat. The whole visit takes around three hours because of the schedule. High Rhine water can cancel sailings.

Nearby

Maria Laach lies west; Koblenz is upstream.