Mount Snowdon
From Tardis Wiki, the free Doctor Who reference
A team from Torchwood One dug up the remains of an alien spacecraft buried at the foot of Mount Snowdon and found Magna-Clamps buried there. (TV: Army of Ghosts)
The Immortality Gate was also found in a ship that had crashed at the foot of Snowdon. It was also recovered by the Torchwood Institute. This might have been the same craft. (TV: The End of Time)
UNIT Base 5 was built into Mount Snowdon. (TV: Death of the Doctor)
