This group sprints to the next corner, tags the group which is waiting, who sprints to the next corner, etc. There is always somebody running. Each group gets about 45-60s rest while waiting for the group in the corner to reach them. Each group should do 3-5 circuits of the pitch. Can be done with or without a ball.
Stairs Find a stairway.
The stadium or coliseum are excellent choices. Pick a distance which will take you anywhere from 30-60 sec to complete. Return to the bottom at an easy pace. Turn and repeat. Start with two sets of 4.