Sentence:  [T]here our camp / Lay pitched that day beneath the sun's wide glare, / Amid the omnipresent desert wastes, / And few men stirred abroad. ... [T]he tents / Sagged lifeless all around their dusky <WSD>cirque</WSD>, / Whose every rope shone burnished in the glare, / And every tent-pin. 
Meaning of the word marked with <WSD> tags:  Something in the shape of a circle or ring, such as a Roman circus.