Quotation from: The Gods of Mars

Written by: Edgar Rice Burroughs

"Come, calots!" cried the rough voice of a guard. "To the slaughter
with you," and roughly we were hustled to the steep incline that
led to the chambers far below which let out upon the arena.

The amphitheatre, like all I had ever seen upon Barsoom, was built
in a large excavation. Only the highest seats, which formed the
low wall surrounding the pit, were above the level of the ground.
The arena itself was far below the surface.