Layover in Vienna

A five-hour layover does not allow enough time to see anything in Vienna.

The only thing you'll be seeing in Vienna is the airport, which is very nice and modern. There's not enough time to go to the city center in my opinion.

The two posts above are correct. Five hours is not enough time to come into the city (which is not by tram, but by train which takes 25-30 minutes to reach the city center).

The express train from the airport to Vienna's main train station runs every half an hour, the ride is 15 minutes. From there you need about 5 minutes to change to subway U1 (red line) and another 5 minutes to go to St. Stephen's Square (Stephansplatz), which is the very center of Vienna.

There you can stroll around, go to a café, etc.

The way back is the same, just in opposite direction. You need a strict time management, be aware of the train schedule, avoid wasting time (i.e. buy train tickets online in advance).

It is also important which flights you are taking, i.e. how early you have to be there for check-in, security checks, etc. Vienna is a pretty "fast" airport, very organized.

Should there be a long queue for the security check, you may use a Fast Track option, either entitled by your credit card or buying a voucher during check-in procedures.
https://viennaairport.com/en/fasttrack

I did something similar about two years ago on my way to Sibiu, Romania.

I met my parents at Vienna airport, and around 10 a.m. we took the train to Vienna main Station (the regular OEBB Train to Wien Hauptbahnhof and not the expensive City Airport Train CAT to Wien Mitte). From there, it’s about a 15-minute walk to the Upper Belvedere Palace. We didn’t go inside the palace, just walked through the park, continued down to the Lower Belvedere, and sat down for a coffee. By noon, we were back at the station and headed to the airport again to easily catch our flight 2 hours later.

Whether it’s worth it is something everyone has to decide for themselves. We went on a sunny day in May, and it was beautiful.

Note: I’m familiar with Vienna, so I knew how to buy tickets, check online the train schedule, find the platform, etc. If it’s your first time there, you’ll need some time to get oriented, so everything may take a bit longer.

Notably, the trains to/from the airport run every 30 minutes, so you will either be lucky or unlucky with timing, if you choose to undertake this adventure.

It is also important to understand whether or not you will need to go through immigration either arriving or departing (or both). Where are you coming from and where are you going? I see from your other posts that you will be going from Lyon to Split on this trip. I'm guessing you are flying in from Split and then going home from Vienna?

Again, I think a visit to the city during a 5 hour layover is ill advised.

That said, let's pretend:

10:00 am - Land in Vienna from Croatia
10:30 am - Exit the airport ready to travel into the city
11:00 am - Arrive in the city center (here I would take an Uber)
11:00 am to 12:00 pm - Spend one hour in the city center (up to you if this is worth your time)
12:00 pm - Take an Uber back to the airport
12:30 pm - Arrive at the airport
13:30 pm - Arrive at your gate after going through security and immigration
15:00 pm - Flight departs

This is all tightly timed and anything here could go wrong which would jeopardize you making your return flight. For example, I took my parents recently to the airport in an Uber and we sat in a traffic jam for 45 minutes. But, if you rely on trains to get to the city center, you won't have any time. It is a risk.

So what to do in that one hour?

I would duck into the St. Stephan's Cathedral (that is where I would have the Uber drop me), walk down the Graben stopping at Zum Goldenen Würstel for a Käsekrainer, turn left on Kohlmarkt, grab a Kaiserschmarrn to go at the Demel window, go left on Reitschulgasse towards the Opera. Get back in an Uber at the Opera. That should take about an hour and show you the main sights of the First District with a little coffeehouse flavor wtih a sausage on the side.

12:30 pm - Arrive at the airport
13:30 pm - Arrive at your gate after going through security and immigration
15:00 pm - Flight departs

This too much ample time, IMHO. You never need a full hour in Vienna between arriving at the airport and reaching your gate. And I have never experienced that boarding started 1½ hours before departure.

I would not take an Uber back to the airport. I guess the likelihood of a traffic jam is greater than the cancellation of a train.

But I agree that a good planning is necessary, including fail-over scenarios (e.g. taking the S7 train instead of the RailJet express). You will need to monitor the train departure times (delay or not delay, that is the question) using a smartphone.