Every canyon leads up to one or more amphitheaters, or cirques, with sheer bare walls hundreds of feet high.
"Grand Teton [Wyoming] National Park"
United States Dept. of the Interior
From the extremity of one of these promontories it is two miles or more across the gulf to the point of the one opposite, and the heads of the amphitheaters are thirteen miles apart.
"The Elements of Geology"
William Harmon Norton
Very possibly these rings, like the Cornish rings used for miracle plays, originated in the stone amphitheaters built by the Romans during their occupation of Britain, buildings occasionally used, even in the sixteenth century, for the performance of plays.
"An Introduction to Shakespeare"
H. N. MacCracken F. E. Pierce W. H. Durham