Devil's Punchbowl

Devil's Punchbowl was a small loch located near Tulloch, Scotland. It was connected to Loch Ness via an underground river. The Fourth Doctor speculated that Zygons were able to secretly send their Skarasen to the North Sea, which was seven miles from Loch Ness, through the river to Devil's Punchbowl, which was much closer to the coast. (TV: Terror of the Zygons)