Although the Pantheon has free entry, apparently there is mass every day from 5:15-6:30pm, and on friday we tried to come in at 6, and waited until 6.45 then left so on saturday around 5, we were determined to get in. The guard was closing the gate, but while he was distracted by a yelling overweight German tourist, we jumped the fence and managed to spend about 5 minutes inside before we had to leave