Burg Hartenfels, Medieval castle in Hartenfels, Germany

Burg Hartenfels is a ruined hilltop castle on a 368-metre basalt cone above the village of Hartenfels in the Westerwald. Its round bergfried, built of slate-like basalt quarry stone, still rises about 23 metres, though it was originally over 28 metres high. The tower has walls 2.35 metres thick, with stairs set inside them, and stands free within the 60 by 40 metre ring wall, of which mainly remnants survive.

Burg Hartenfels was first documented in 1249, when Countess Mechthild von Sayn sold it to the Archbishop of Trier. It guarded the Hohe Straße, the trade route between Frankfurt and Cologne, today the B8. Destroyed in the 15th century and rebuilt, it was finally razed in 1594 by Count Wilhelm von Nassau and never rebuilt.

Locals call the ruin "Harbelser Schmanddippe", after the dialect word for a butter churn. One story says a French soldier asked a woman the tower's name and she mistook the question for the churn; another explanation is simply the tower's shape. The castle also guarded the Hohe Straße, the medieval trade road between Frankfurt and Cologne, now the B8.

The ruin is freely accessible and can be explored during daylight hours; there is no admission charge. The bergfried, about 23 metres high today, cannot be climbed, so the visit stays at ground level among the wall remains of the roughly 60 by 40 metre site. The basalt cone and uneven ruins call for sturdy shoes.

Locals call the ruin "Harbelser Schmanddippe", after a butter churn: one story says a French soldier asked a woman the tower's name and she mistook the question for the churn's dialect word, though the tower's shape may simply have prompted it. The round bergfried still rises about 23 m, from an original height of over 28 m, and cannot be climbed.