The Appia Antica is open to scooter and automobile traffic. Vendors will tell you that Scooters are allowed into most ZTL areas and pretty much everywhere except "pedestrian only" zones. For some Romans this includes sidewalks & crosswalks! I've never received a summons for riding a scooter in a ZTL. That said, the Appia Antica is closed to ALL traffic (including scooters) on Sundays, as it becomes a pedestrian only walkway. Note that riding a scooter on Appia Antica is like riding a waverunner - the dips and potholes on the old cobblestone road could loosen your fillings! We've taken that ride many times on our scooter(s).  If you're renting a scooter in Rome I would caution you. Having previous motorcycle experience is very helpful. Also, do not get an underpowered scooter. For two people, rent a 125cc which is the largest you can drive in Italy without an Italian motorcycle license. You'll need the 125cc horsepower to get out of trouble and up some of the hills! Get one with a "bauletto" (storage box for 2nd helmet) and windshield. If you've never ridden a bike before, Rome IS PROBABLY NOT the place to learn! And even those with experience often shake their heads at Roman drivers. The biggest challenges seem to be other motorini drivers, taxis, buses, potholes, rough roads, people in crosswalks, confusing signage, and cars - in that order!!!!

Depending on the season and the vendor, rentals usually start around E50 a day for a 125cc. Some vendors will ask for an IDP (International Drivers Permit) but most do not... If you have an "incidente" you'd better have an IDP! If you Google Rome scooters you will see many, many vendors!