Walling

Nor was this all; seeing something projecting through the soil at the bottom of the bared patch of walling, I removed the loose earth with my hands, and revealed a huge stone ring, a foot or more in diameter, and about three inches thick.

“All three,” says Dr. Schliemann, “were unusually large, and appeared to have been forced into the small space of only 5 feet 6 inches, left for them between the inner wallings […]

The longer the platform, the more signs, fencing, walling, lighting, drainage and public address systems (and so on) are needed.