Gronauer Castle (Ruin) (Salzböden)

The Old Gronau Castle is a castle ruin in the northern Krofdorfer Forst near Krofdorf-Gleiberg (Wettenberg municipality), close to the village of Salzböden (a district of Lollar), in the Gießen district in Central Hesse.

The remains of the former hilltop castle crown the so-called "Schloßberg" (Castle Hill), a greywacke spur about 20 meters above the river Salzböde, which originates in front of the Schelder Wald above Hartenrod and flows into the Lahn from the right near Odenhausen.

Directly below the Old Gronau Castle, in the meadow valley of the Salzböde, there was an important road ford.

About one to two kilometers away, there was an important traffic junction at that time. Here, the great Upper Hessian South-North road, coming from Wetzlar, which absorbed the Herborn "Rennweg" southwest of the Dünsberg, was joined by the Wetterau Wine Road, a summer shortcut that crossed the Lahn below Gießen at the "Wolfsfurt" of Selters (now a deserted village); in contrast, the Rennweg, together with the Kirchberg "Lange Hessen" branching off not far to Amöneburg, formed a distinct West-East axis, while a northern cross-connection from the Rothaargebirge to the Vogelsberg must also have passed through.

Moreover, the Schloßberg was located on these important elevated routes in such a way between the similarly fortified imperial estate outposts of Großen-Linden, Wetzlar (with Altenburg), Herborn (with castle), Wetter (with Kesterburg), and Amöneburg, that the rows of the other, mostly similarly situated and structured places, with proper knowledge of the contemporary roads, almost automatically resulted in distances of 25-30 km from each other; however, some suitably located old farmsteads and occasionally ancient regional fortresses also appear to be incorporated.

The early Carolingian road fortress was presumably built in its first design around 720 AD by the Mayor of the Palace, Charles Martel.

During Charlemagne's early Saxon campaigns from 772 AD onwards, the complex was evidently modernized.

The function of the complex is presumably a staging post or a protective castle for the old long-distance routes passing through here.

Presumably due to the construction of Gleiberg Castle, the Old Gronau Castle was abandoned and fell into disrepair.

In April 1936, for the State Office and at the expense of the Archaeological Institute of the German Reich (Berlin), the survey and excavations at the Old Gronau Castle began.

Of the former castle complex, remains of the curtain wall, a building, and a tower are still visible.