Tyllwyd campsite on Saturday afternoon:
18th century illustration of the Robbers' Cave. The rustic bridge has gone but the Cave is still there as shown; it is now approached from the far right of the illustration, via a path above the left bank of the river (a steep tributary of the Ystwyth):
It's a short, dark, wet tunnel at the end of which you emerge above a drop to a plunge pool with a waterfall opposite, open to the sky. Here you can just make out the far end of the tunnel through the spray, with the waterfall just right of the student on the left:
This is a better photograph taken by a better photographer with a better camera on a drier day!