Through the "Untertor" (lower gate) the through traffic probably moved already before the granting of the town charter (1344).
It is likely that, even before the town rights were granted in 1344, traffic passed through Dillenburg’s north and south gates to the trade fair cities of Frankfurt (to the south) and Cologne (to the west).
The first major renovations took place in 1594. Princess Isabella, wife of the last Dillenburg Prince Christian, created the current building complex by structurally joining the two houses next to the gate in 1737.
The Princess, who had fallen out with her husband, lived in this ‘city palace’ until the time of her death. This building has therefore also been known as the ‘Princess’s House’ and later, when several state authorities were based here, the ‘Collegiate Building’.
In the 18th century, the area around the south gate was home to members of the upper classes.
Following extensive renovation, the building has contained private apartments and the public library since 2009.