The Kallektuffquell, a mossy limestone spring in the Black Ernz valley

Most people come to the Mullerthal for the big sandstone clefts and the gorges. The Kallektuffquell is the opposite of that, a small, quiet spot, and for its size I’d say it’s the most striking thing in the valley. Very clear, lime-rich water slides over a ledge of rock thick with moss and gathers in a little basin. visitluxembourg picks out the colours of the water and the stone and the number of different mosses, and honestly that’s the whole point of coming.

Finding it in the Black Ernz valley

The spring lies beside the CR 121 road in the Black Ernz valley, at Breidweiler, one of the villages that make up the commune of Consdorf. There’s woodland all around and no village on the doorstep. Without a car, the nearest bus stop is Müllerthal Schiessentümpel (Parking), 1.4 km away, and since buses are free throughout Luxembourg the trip out from the capital costs nothing once you’ve landed at Findel or arrived by train.

The official listing gives the name in three languages, source de tuffeau, Kalktuffquelle and travertine source. In plain English, it’s a tufa spring, water loaded with lime, which is why the rock it runs over looks crusted and oddly coloured.

Route 3 or path W7?

On the Mullerthal Trail it’s Route 3, the castles loop, that brings you here. Coming down from Blumenthal, the path crosses the Marscherwald, an open beech wood, then the Black Ernz, and reaches the spring along a 700 m wooden boardwalk. It carries on to the Schiessentümpel, the waterfall with the little stone bridge, and about a kilometre later arrives back in Müllerthal. The full loop is 37.7 km, which the operator estimates at 11 hours 5 minutes and suggests splitting over two days.

The shorter option is local path W7, 10.2 km from the Heringer Millen, the old mill at Müllerthal that now works as a visitor centre with a restaurant. The region’s local paths are circular, so you finish where you started.

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How I’d plan the day

I wouldn’t come just for a photo and leave. With a single day, I’d walk W7 in the morning with a long pause at the spring, have lunch at the Heringer Millen and keep the afternoon for the Kuelscheier, the pitch-dark rock tunnel near Consdorf on Route 2, where you’ll need a torch.

If you’re doing the whole of Route 3, the spring comes near the end of the loop when you set off from Müllerthal towards Beaufort, so your legs will be tired by then. Build in time to stop.

What the listing leaves out

There are no opening hours and no admission charge on the listing, because this is a spot in the woods reached by paths. Walking boots and some water are all it asks of you. The Mullerthal Trail site says the colours change with each season, so I don’t think there’s a bad month for it, but I’d check its path status page first, as it flags closures. One piece of common sense you won’t find on any listing is to keep to the boardwalk and the path, because the moss that gives the place its colour is the first thing to suffer from trampling.

To sleep close to everything, search places to stay in Berdorf on Expedia and filter by area before price.

If you are short on time, see the best tours in Kallektuffquell and pick one that fits your day.

Where the bus does not go, a car does: compare car hire in Luxembourg before you arrive rather than at the desk.

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