Madonna -- When in Rome ... Flash Your Ass!

After flashing her nipple in Turkey the other day, Madonna continued to strip down on the latest stop of her body part peep show tour by showing off her mother-of-four butt in Italy on Tuesday.

While performing her hit song "Human Nature" again, the Queen of Pop unzipped her pants and exposed her lacy thong-clad 53-year-old taut backside to the crowd at Rome's Stadio Olimpico.