In Rome I was accompanied by several teens in a tour group and they had NO interest in the Sistine Chapel or anything cultural for that matter.

Seriously, with 24 hours think of gelato at the Trevi fountain, walking down the Spanish steps and on to Piazza Navonne, sitting in cafes, a ride on a Vespa, etc. Ask the teens what they think of when they think of Rome. They will be back and can see the major sites some other time. For now, enjoy the city!