How does Luigi Barzini use imagery in The Italians?

Imagery:

"There are sultry days in July and August when the cities, emptied by the natives, are almost completely taken over by the swarms of dusty and perspiring foreigners. During the siesta hour, when even the carriage horses sleep under their straw hats, the relentless tourists finally slow down. They bivouac everywhere. They recline on park benches, kerbstones, the stone brims of fountains, or ancient ruins. They place their heads over their crossed arms on café tables for a siesta among the empty bottles, the dirty napkins, and the recently purchased souvenirs. They then really look like a tired and bedraggled army after a fatiguing battle, who have occupied a city abandoned by their fleeing enemy. They have conquered. The place is theirs."