Apci Tengerszem, also known as Széleskő Quarry Lake, is located in the valley of the Zagyva River near the village of Apc. The settlement dates back to the Árpád era, with its first written records from 1246, and today has a population of fewer than three thousand inhabitants. Despite its small size, the surrounding landscape offers excellent hiking opportunities, and the former quarry lake has become an increasingly popular destination for nature enthusiasts.

The lake and its surrounding forests were designated a locally protected nature reserve in 1995. The quarry lake is deep, with steep rock walls surrounding its shoreline. In good weather, visitors often rest along the shore, while the surrounding cliffs offer impressive viewpoints. A narrow trail runs around the lake along the cliffs, although this route is not recommended during wet conditions due to slippery surfaces.

The site provided an ideal environment for testing UNEXMIN GeoRobotics’ new ROV, the ugROV-1. Designed with a compact frame, the robot is capable of operating in highly constrained and obstructed environments, such as abandoned flooded mines. Developed during the summer of 2025, ugROV-1 was first tested under real conditions at the Apc quarry lake, successfully demonstrating its capabilities and laying the foundation for further development toward 3D underwater mapping and photogrammetric surveys.