Mount Snowdon

Mount Snowdon was the tallest mountain in Wales, at a height of around 1,085 metres (3,560 feet). A team from Torchwood 1 dug up the remains of an alien spacecraft buried at the foot of Snowdon and found Magna-Clamps buried there. (DW: 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. (DW: The End of Time)

UNIT Base 5 was built into Mount Snowdon. (SJA: Death of the Doctor)