Pont-yr-Daf (Dragon's bridge?) was submerged when the Llwyn-Onn reservoir was completed in the 20s. it's currently visible as the reservoir is virtually empty. currently the water level is probably 25 to 30 foot below the full water level. the top walls are long since gone, but what it left is still surprisingly solid. interesting to see the inside of the bridge, now the top surface has partly washed away