Somoskő — Šomoška in Slovak — is the second of the basalt-perched castles outside Salgótarján and arguably the more atmospheric. It is restored more thoroughly than Salgó, with the bastion roofed and the walls intact enough to wander, and the basalt waterfall just below the castle is a small geological wonder on its own. The hexagonal columns of the flow, frozen mid-cascade down the hillside, are an unmistakable sight.
The castle lies a few hundred metres on the Slovak side of the border, but the village of Somoskőújfalu on the Hungarian side is where you start. Bring your passport or ID; the crossing is unmanned but EU rules apply.