An archival research team brought the final answers two days later with faded parchment land plans dating back to the late 1700s. The ancient maps revealed that an unregistered, pre-industrial salt mine had once operated deep within the hill before being abruptly abandoned and sealed out of local memory.
Geological analysis confirmed the rain-driven process: every time it rained on the hillside, groundwater filtered through the rich salt deposits inside the tunnel ceiling. The salty brine trickled down and seeped into the porous brickwork. As the moisture evaporated into the warm barn air, pure mineral salt crystallized on the surface, creating an irresistible salt lick for the calves.
Even more surprising was the map's layout: the oldest stone section of Robert's barn had originally been built as the mine's surface portal over 250 years ago. Today, the calf is fully recovered, the tunnel entrance is safely secured behind a locked iron gate, and an enlarged copy of the 1780 mine plan hangs beside the barn door—a permanent reminder of the underground world uncovered by a few stubborn calves.