Gerenna Castle, Castle ruin on Gerenna Peak near Szilvásvárad, Hungary.

Gerenna Castle is a medieval fortification ruin situated on a hilltop near Szilvásvárad in Heves County. The remaining stone walls and foundations sit on elevated terrain, offering views across the forested and agricultural landscape surrounding the site.

The ring-shaped earthwork was built by Slavs living in the area before the Hungarian conquest, and it was used in the 14th and 15th centuries; its layout suggests it was built later than nearby Éleskő Castle. Medieval records are uncertain: tradition holds it was a hunting lodge of Louis the Great and later used by King Matthias. How it was destroyed is unknown, and today its foundation walls are barely visible.

The ruins display construction features typical of medieval Hungarian fortifications, showing how builders designed defensive structures of that era. Walking among the remains reveals the practical choices made for protecting the settlement below.

The ruins are accessible via marked hiking paths from Szilvásvárad that wind through the forested and hilly terrain. Information boards at the site explain the history and architectural significance of the location.

The castle's name comes from the fortress that once stood here, but almost nothing of it survives: only its foundation walls are barely visible today. The small ring-shaped earthwork is surrounded on all but its steep eastern side by a 3–4 m wide, roughly 2 m deep ditch filled with rubble. Its entrance was probably on the easier western side, reached by a wooden bridge over the ditch to a drawbridge gate.