A Straight Corridor Beginning And Ending At The Same Place

Storm and Lockridge, now on foot and in daylight, approach a dolmen on a small hill. Lockridge knows that:

"...the chamber within...had once been buried under heaped earth, of which only this mound was left...."
-Poul Anderson, The Corridors Of Time, CHAPTER THREE, p. 24.

When Storm has raised a circle of earth, they descend a spiral ramp, Storm closing the entrance behind them. They enter a long room and pass through an immaterial veil into an impossibly long corridor along which they travel on a moving platform at an estimated thirty miles per hour. After about half an hour, they leave the platform, step through another veil, pass through another long room, up another spiral ramp and out another turf trapdoor. It is night.

Anderson writes that:

"...the moundside now covered the dolmen, up to the capstone, with a rude wooden door beneath." (p. 31)

- as if we are to understand that it is the same dolmen - which it is. Time travel has occurred by a much more roundabout route than in either the Time Patrol series or There Will Be Time.