The Man Who Awoke by Laurence Manning

With a curt nod, he pressed a button and was lifted rapidly up to his seat under the dome. Winters felt the platform shake and roll beneath him as the huge structure made its way over the ground. After half an hour, the floor ceased its sickening lurching and the steel door flew open. Winters gazed at it, fascinated, and there entered the cablelike tentacle! With a cry he sprang away, but the steel coil whipped itself around him like lightning and he was drawn out of the door and lowered giddily to the ground far beneath.

He stood on a small slope and before him rose the walls of a city. They were about fifty feet in height and perhaps a quarter of a mile long-silver gray with the sheen of some metal worked into the very stone of the structure. The tentacle had released him, but rested on the ground behind, as if to prevent his escape. He stood and puzzled what to do when a huge booming roar came down to him from the skies: