The Stone Bridge

"We had been following the narrow path for hours, climbing with difficulty and without stopping.
At our side the stream roared, a dozen meters below us, when we see the bridge, powerful and intact, ready to allow travelers to reach on the opposite side of the gorge.
What a curious place though: from a steep path we can go down to the river and, on the other side, another path allows you to reach the entrance of a cave.
What will be in there? The dwarves did not build anything without a reason. "