Dreienburg Castle (Ruin) (Lautenhausen)

The Dreienburg castle ruin (popularly known as Alter Keller) is a castle ruin in the southeast part of the Dreienberg in the district of the Hessian municipality of Friedewald in the Hersfeld-Rotenburg district.

The Dreienburg castle ruin is located in the Kuppenrhön, a part of the Rhön low mountain range, near Lautenhausen (southeastern district of Friedewald) on the eastern slope of the Linsenkuppe () and thus on the southeast part of the Dreienberg (max. ), the northernmost mountain of the Rhön.

The spur of land, on which the ruin is located at an altitude of around , juts eastward into the valley of the Stärkelsbach, a western tributary of the Werra. From here, nowadays only through the trees, one has a wide view into the Werra valley and to the Kuppenrhön (including Landeck Castle). Lautenhausen is located northeast, about 105 m below the ruin.

The period of origin of the castle complex, which was probably commissioned by the Hersfeld Abbey as a protective castle against Hesse, is not known.

The first documented mention took place in 1257, when the lord of the castle Hertwig von Drigenberg was named. In 1296, a Wolprat de Drigenberck was mentioned. The ruin was last mentioned in 1641.

Of the Dreienburg castle ruin, which is nowadays designated as a cultural monument, wall remains of the watchtower and the neck ditch are still visible.