Asseburg, Medieval castle ruin in Wittmar, Germany.

Asseburg is a castle ruin on the southern ridge of the Asse hill, near the village of Wittmar in Lower Saxony. Remaining walls and earthwork traces outline the original layout of a medieval hilltop fortress built on elevated terrain.

Gunzelin of Wolfenbüttel began building the castle between 1218 and 1223 as a Ganerbenburg held by several co-owners. In 1254 Duke Albert I of Brunswick-Lüneburg besieged it for three years; it was handed over in 1258 for 400 gold marks. The garrison burned it on 12 August 1492, and it has been a ruin since.

The name Asseburg comes from the Asse, the ridge on which the fortress was built. The stone walls still standing today give a sense of how dominant this structure once was over the surrounding countryside.

The ruins can be reached on foot from the Asseparkplatz car park in Wittmar, with trails that are clearly marked. The ground on the ridge is uneven, so sturdy footwear makes the walk more comfortable.

When Duke Henry IV demanded the fortress back in 1492, the garrison set it on fire before retreating rather than surrender it. The fire left so little standing that no one ever attempted to rebuild it.