From Shelley’s preface to Prometheus Unbound:
This Poem was chiefly written upon the mountainous ruins of the Baths of Caracalla, among the flowery glades, and thickets of odoriferous blossoming trees, which are extended in ever winding labyrinths upon its immense platforms and dizzy arches suspended in the air. The bright blue sky of Rome, and the effect of the vigorous awakening spring in that divinest climate, and the new life with which it drenches the spirits even to intoxication, were the inspiration of this drama.
Many years ago I saw an outdoor ballet in the same ruins of those baths. They also feature in a scene in what I without hesitation find the greatest movie of the past several decades – The Great Beauty.