I need a rental car for a few hours to visit the Roman city of Carnuntum on the Danube 45 km east of Vienna. Instead of flying, seeing nothing en route then renting a car for a few hours or taking the train, seeing a lot but then having to rent and drive out of Vienna, .... I wondered about one-way car rental - picked up in central Munich and dropped at my hotel in central Vienna. We could see something en route, stop somewhere, not waste time getting to and from airports at either end, by-pass Vienna going through to Carnuntum, have the car for luggage transport door to hotel door, and probably not much more expensive than two air or train tickets.

Any advice? Can you do a one-day one-way rental?

Train/ Rental car:
I see no advantage in avoiding to drive out/in central Vienna vs. drive out central Munich/ in central Vienna.
Rail connections are good, with the new RailJet services between Munich and Vienna.

Plane / Rental car:
Carnuntum is just some 20km east of the airport and you don't have to go thru Vienna to get there.

Rental car:
Probably the slowest way to travel, on often busy motorways.
Check viamichelin.com for times, and a quote on potential costs for gas.
There is a lot "to see" en route, indeed. But if you plan it as a trip during daytime, you will not have much time to see anything en-route if you want to spend time at Carnuntum, and have to go back to central Vienna after that.

Unless there is convenient public transportation to Carnuntum from Vienna Westbahnhof or the Airport, I would say that in this very specific case (and given that you can get a good airfare), the combination of plane + rental car will make most sense. Check airberlin.com for cheap fares from Munich to Vienna.

Hi ser,
You can expect a pretty stiff drop off fee for picking up in Germany and dropping off in Austria.

How much is a "stiff" fee? I have rented in one coutry and dropped off in another and do not remember the fee to be crippling.

But I have not done this in quite a few years so would be interested in hearing what people have paid for this recently. (Another travel site mentions a fee of 100-200 euro.)

I have not checked each and every rental company, but Sixt charges around € 120 for one-way rentals for a compact between Germany and Austria. The price for a one day rental of a compact would be €80 (you should be able to do bit cheaper if you use resellers).
Add € 50 for gas and toll to drive from Munich to Vienna.

So am I understanding correctly that the upcharge for drop off in Vienna would be 40 Euro?
(Difference between 120 and 80??)

No, the total charge for the rental would be 200€.

So drop-off fee of about 120Euro?

That is about what I remembered from the last time I did this. Thanks very much! So this can be an option for the next dual-country trip!