The Druid ruins of Rothmore are located in England.
The Scooby-Doo Show
In England, Jimmy Pelton, a famous tennis star, and his trainer, Nick Thomas, were jogging one night, training for Jimmy's tennis match at Wimbledon the following morning, when they stumble upon the ancient Druid ruins of Rothmore. There they discover some sort of ancient staff and then they encounter a warlock named Anthos, along with his demon hound, who claimed to have awoken from his life-long sleep to fulfill the curse upon the Pelton family. The warlock tells Jimmy that as long as he has the cursed staff, he is doomed. Jimmy and Nick fled. Fred, Daphne, Velma, Shaggy and Scooby were touring England at the same time, and happen to be driving nearby the ancient ruins of Rothmore. Nick and Jimmy stumbled onto the road and are picked up in the Mystery Machine. Nick and Jimmy told the gang about their attack by the warlock Anthos, and the gang and Jimmy and Nick drive to Jimmy's mansion.