We will be arriving in Rome on Oct 2 and leaving on Oct 4. What to do in only one day? We are 2 adults, no children.

It depends on your interests. If you like museums you could go to the Sisitne Chapel. If you want to take it easy you can just stroll around the Piazza di Spagna, Via Condotti, Via del Corso, Piazza Navona area, shopping and people watching in Piazza Navona drinking a cappuccino or something. If you like history you couls go to the Colusseum and Forum and eat at Magna Roma, the restaurant near the Colusseum that offers meals of the ancient roman recipes. The solutions are endless... Could you give us some more info about your interests?

Cry in your chianti that you only have one day.

But...Pantheon - 20 minutes, Trevi Fountain - 30 minutes, St. Peters - 1 hour, Piazza dei Poppolo - 20 minutes, Spanish Steps - 30 minutes...you get the drift.

You can race through many of the things. You'll be sad you missed an in-depth look at the Forums or the Colosseum. Plan it out and hit the road...don't dilly dally and you'll see more than what you think you can.

if I had one day in Rome:
i will start with the Coliseum,
from there to the Vatican visit St Peter
check the line for Sixtine Chappel if not too crowded then visit otherwise, leave it for next time.
go for lunch in Piazza del popolo,
A restaurant call La Bolognese, from there I will walk to the Piazza dÉspagna walk the steps and have a coffe in Via Veneto do some window shopping.
Depending on time probably back to the hotel enjoy the room and the facilities Dinner at Piazza Nabonna.
After dinner i leave it up to you.

The smartest thing you could do with limited time is to hire a personal tour guide. We were in the same situation last year and found a great tour service called Vatican Tours & Beyond (they have a website). They were excellent. We toured the Vatican in the morning with a private guide and then toured the city in their vehicle in the afternoon. It made the trip so much better having a well trained guide to tell us about everything we were seeing. If you try to do on your own you'll either miss a great deal or not really understand what you're looking at.

Following up the previous post, it's a no-brainer to me: Take an all-day tour of some sort.