Jet Lag!

What time do you get in and where are you staying? Asking so people can give you suggestions in your neighborhood.

My usual plan is to drop off my bags at my hotel, walk/walk/walk in the sunshine, have a meal then head back to the hotel. You'll get differing opinions but I often take a nap for about 1.5 hours (I set an alarm) when I can get into my room, then shower and head back outside. I'm ready for bed at my "normal" time.

Many here will completely advise against this but it works well for me when I'm on my own and I'm good to go the next day. You'll have to decide what will work best for you.

Take it easy, stroll around in the immediate neighborhood to get your bearings, and soak in the sun outside as much as you can - it really helps with jet lag.

When in Italy in addition to staying out in the sunshine and fresh air I have a coffee corretto. That is espresso with grappa and a couple sugars &/or some brandy. Really wakes me up and gives me the jolt I need to stay awake. I try to stay up to a usual bedtime, but never go to bed before 8 or 9pm.

Go to your hotel, check in and drop your bags, then stroll around the neighborhood. 1 pm stop in some place and have lunch. Afterward, you should be able to get into your room.

Most often we arrive Europe in the am. Last time 7:30 am. If we are not at our destination, we will take the train (never drive). One benefit of that is that we will occasionally doze for just a bit which can refresh some. We avoid getting too comfortable and tend to stroll and do light sightseeing. Most often, our hotel room has been available, when it hasn't, the hotel will store our things. We don't do any major sights that require paid tickets the first day. We might sit in a cafe for a bit, no alcohol or caffeine. No napping. We try for an "earlish" dinner. A glass or two of wine/beer at dinner. We go to bed at about 9pm and get up no later than 8am. We adjust our time to the destination time the day we are leaving on the trip. When possible, we will try to adjust bedtimes for about the week prior to the trip. We take melatonin in the evenings at about 9pm, per the time zone we are traveling in. We are typically so excited for our travels that we can "power through" that first day. This has worked well for us.

If we're talking about just trying to kill a few hours until the room becomes available then I agree that dropping your bags at your hotel, setting off on foot, and generally gutting it out is probably your best option.
If we're talking about a very early arrival at FCO, sleep deprived after the long flight from the US and faced with the prospect of having to stagger around for 8 hours, then you could consider just booking your room for the night before so that it's "ready on arrival". You might find the extra cost well worth it if all you want to do is check in, take a shower, and maybe take a short nap in order to feel human again. Helps us minimize the chances of catching cold (or worse) in our run down state if we baby ourselves like that. Might work for you too.

We do pretty much what everyone else does: have the hotel store the bags, head off for a bracing shot of coffee, walk until check-in, and then walk some more until we're ready for an early-ish bedtime.. We don't eat a sit-down meal on arrival day as we're usually not hungry from all the sitting on the plane, and never nap so that we can get onto "Italy Time" as quickly as possible.

We do, however, have a couple of adult beverages at a neighborhood bar before hitting the rack. If our accommodation has a bar and terrace, that much the better! 🍺🍷

Do not take a nap. Do not take a nap. Do not take a nap. Do not take a nap. Do not take a nap.

"Do not take a nap."
Have to respectfully disagree with that advice. If you need a short nap upon arrival to refresh and recharge then do it. Some people can indeed gut it out with no ill effects - not us, especially as we've gotten older. Nothing wrong with babying yourself if it helps keep you healthy.

Also disagree with “do not take a nap.” We generally follow Pam’s itinerary, including a short nap. Whatever works for you. But definitely get out and walk!

Also disagree with “do not take a nap.”

I find 45-60 minutes gives me a quick charge and lets me get to bed at 'local bedtime' and sleep well.

For me, the 90 minutes Pam takes, would mess up my internal clock too much.

I usually catch some sleep on the plane. Even in "regular life" I try not to nap, it messes up my sleep at night. If I do nap, I was advised to keep it to about 20 minutes. When traveling if we do nap, we again keep it to about 20 minutes. Sometimes my husband will doze off somewhere, and then I let him sleep for just a bit. I think this all depends on the person, age and regular sleep patterns. All a person can do is get varying advice from experts and fellow travelers and then figure out what works.