As well as flights to Flughafen Wien, you may want to consider travelling by train. Eurostar to Brussels, then Thalys or DB ICE to Köln, and finally the ÖBB Nightjet to Vienna. Your go-to guide is at http://www.seat61.com/Austria.htm
One bonus of booking a sleeper is access to the First Class lounge at Vienna on arrival, a chance to relax and freshen up before heading to your hotel. In fact, first class travel within Austria is usually only €5 or €10 more than standard, and you can then use the lounges at both ends of your journey - free drinks, food, wifi, and a space to relax.
Check prices at both www.bahn.de and www.oebb.at
Getting into town:
If coming from the airport, the S7 train (€4) and the CAT train (€11) both stop at Wien Mitte, which is an interchange with the U-Bahn system. Alternatively you can get the Railjet train (€4) to the Hauptbahnhof.
The Hauptbahnhof is also out of town, on the U1 line, so it is easy to get into the city and change.
You're in luck! We stayed at 3 different hotels and would recommend all of them.
Hilton Vienna Plaza
In the heart of town, with very easy access to Metro and trams, this luxury hotel is the priciest, but is absolutely beautiful, has a great bar, and the rooms are splendid.
Hilton Vienna Danube Waterfront
This stylish hotel is right on the Danube, so has amazing views. In the summer you can use the outdoor pool. It's a little out beyond Prater, so you have to get the U-Bahn to Stadion, then walk (following the very clear signs) for less than 10 minutes through housing to a bridge over the Handelskai main road. It's a very safe area and has a local supermarket on the way for provisions.
Park Inn Uno City
This was our cheap hotel taking advantage of a weekend deal, but in fact it was just perfect in terms of service and rest. Uno City is a modern area on an island on the east of the Danube, with futuristic U-Bahn stations. The hotel is less than 10 minutes from Kaisermuhlen VIC station, and its rooms are behind the hotel front, in a very peaceful courtyard.
We don't often buy city passes, and never go on the open-topped buses, but for Vienna we made an exception. Buy your pass in the Opernpassage, near the U-Bahn concourse at Opera station.
From 1 day for €70 up to 3 days for €110, it includes free travel on U-Bahn and city buses (though not the train to the airport). But you also get free, unlimited Hop On Hop Off bus access, which is the only way to Schönbrunn, and is a quick way of getting around the city without trying to find underground stations (which are few in the central pedestrianised area).
And then you get entry to 60 attractions: we used it for Ferris Wheel (€10), Cathedral (€5), Belvedere (€20), Schönbrunn (€15), City Cruise (€20 - AVOID, see below), Museum of Art History (€15), National Library (€7), Literature Museum (€7), Mozarthaus (€11), Jewish Museum (€10), Museum of Modern Art (€11), Freud Museum (€10), Transport Museum (€8) and the Prater Museum (€5). And that was in 3 days!
The full list is here: https://www.viennapass.com/vienna-attractions/
If you just want to get a travel pass, then the week-long pass runs Monday to Sunday and is worth it if arriving near the start of the week. It's under €20. Day passes are around €8. More info at http://www.wienerlinien.at/eportal3/ep/channelView.do/pageTypeId/66533/channelId/-47382
Bitzinger Würstelstand Albertina
Operngasse, just behind the Theatre and the Opera
The best hotdog stand in the city. The rest are all pretty good, but this one has the best sausage selection, the best beer selection, and the best service
Also at the Ferris Wheel in Prater
Backup plan: the hotdog stand on Kupferschmiedgasse
In the back streets near Judenplatz, we sought out this little bar that serves the best Fladenbroten (filled pita breads) in town. They have 40 different fillings and a great beer selection.
A market half a mile long, with food stalls, small eateries, and sit-down restaurants, all in the middle of a busy street. You can buy anything here, the problem is deciding where to have lunch!
We're not going to list all the places we used the Vienna Pass for! Here are some tips for seeing a different selection.
Not much of a looker from the outside, but the architectural detail inside is amazing, it has a well-designed extension, plus the smallest lift you have ever seen. Temporary exhibitions on aspects of Viennese life, plus maps and models of the city in development.
St Stephen's Cathedral
An incredible building, for many the highlight of Vienna, with a decorated roof, and two towers, one accessible by stairs, the other by a lift. The tour takes in views of the organ loft and cathedral treasures.
Not just for fans of the film The Third Man, this Ferris Wheel and amusement park date back to the 1760s, though they have been renovated since then. You arrive at Praterstern station, and follow the crowds into the park. It's worth getting tickets for the Wheel online, though you still have to queue. Some people book a private compartment to have dinner on the wheel, but you have a lot of eyes on you! Amazing views at any time, but twilight as the city dims and the lights come up below, is a great time to travel.
This distinctive yellow tram is the only one to completely circumnavigate the Ring. It runs every 30 minutes. Board at Schwedenplatz and pay the €8 on board - travel passes not accepted.
Four big hitters here - Architekturzentrum Wien, Kunsthalle Wien, LEOPOLD MUSEUM, mumok - plus 10 cafes and 9 shops. Plenty of lounging space in the courtyards.
AVOID. Of all the cities and boats we've been on, this is the one time we say no go. The DDSG boats from Schwedenplatz do not go on the beautiful Blue Danube. They go along a narrow canal backed onto by graffitied walls and office buildings. Just as you get within sight of the Danube, it turns around and heads back. It's not even a nice canal like in Copenhagen. Wait until you get to Salzburg. Now THAT'S a boat trip.
Getting There (and Back):
Travelling on ÖBB, we'd again recommend first class travel as it's not that much more expensive, and you can use the lounges at both ends of your journey. www.oebb.at
There is another train company, Westbahn, which has a fixed price that you can buy on the train without reservation. It depends how organised you want to be. Note these leave from Westbahnhof, not Hauptbahnhof. https://westbahn.at/en
Again, a go-to guide is http://www.seat61.com/trains-and-routes/vienna-to-salzburg-by-train.htm
A final tip. If you plan to break your journey, eg at Linz (see below), it may be cheaper to buy a through ticket, and just get off at Linz. There's no barriers to stop you doing this. Obviously you'd need a separate ticket for the rest of your journey, but it's still an economy.
Another good value card, €27 for 24 hours, including buses, free boat trip, and entry to lots of museums, some of which are worthwhile.
Holiday Inn Salzburg
A 15 minute walk from the east side of Salzburg Hauptbahnhof, along a safe main road, served by buses 12 (to the station) and 2 (to the centre of town). Friendly, spacious, and quiet.
St Peter's Bakery
Salzburg's oldest bakery, cooking sourdough in the wood-fired oven, using wheat ground by the waterwheel
Festung Hohensalzburg (Fortress and Funicular)
open from 9.30am, worth getting there early for a prompt ride up to the fortress and lots of viewpoints, Regency State Rooms and the marionette museum
Weihnachtsmuseum (Christmas Museum)
opposite the Mozart statue, this collection of German and other Christmas decorations and traditions was accumulated over 40 years. Unsurprisingly there is also a Christmas shop!
Mozart Birthplace and Mozart Residence
Getreidegasse 9 and Makartplatz 8
if two Mozart museums in Vienna weren't enough, there are another two here!
Museum of Modern Art - high and low
take the Mönschsberg Elevator for clifftop views across the city and the river and the upper museum. The lower one is behind the Franciscan church in the Old Town. The lift costs money but is cheaper with a museum ticket, valid at both venues.
Dating from 1829, this panorama shows Salzburg and the surrounding countryside, and went on tour around Europe at the height of the panorama craze
Free with the Salzburg Card, these trips are very popular so you will want to book one early in the day and come back later. If there aren't cheap spaces, you can upgrade to A Class, which gets you into a different queue, and better seats on the boat, behind a velvet rope! Only €3 extra!
The boat gives excellent views up and down the river, and it shows off its speedboat motors right at the end!
If you want to explore the Tirol region of Austria, Innsbruck is a great place to start. The train journey from Salzburg is mostly in Germany so have your passport handy, but you won't need it. Railjet trains make it in under 2 hours, and run every hour.
The Hauptbahnhof is to the east of the city, and it is easy to get about on foot. The biggest highlights are the Hofkirche (a memorial tomb surrounded by 28 giant bronze statues), the Golden Roof (Goldenes Dachl) and the Cathedral (Dom).
There's an even bigger attraction that you can get to with zero effort, and it's 2,256 metres high! Right from the centre of town (find Congress station) there is a cable train that goes under the river, then up to 860 metres stopping at Hungerburg. From there you can take a series of cable cars to Seegrube and Hafelekar, a short walk from the summit. There are views over Innsbruck itself, and the Karwendel national park.
We recommend lunch at the Seegrube restaurant, on the first floor (not the self-service cafe). The views from there are amazing, and on a warm day you can dine outside. We had 2 types of soup with meatballs, and then Hünnerbrust and Käsespätzle for some local flavour.
Buy your tickets at Congress station, €30 isn't cheap but they are the best and easiest views in Austria!
This fortress town is on the border of Austria and Germany, and in fact the train journey is mostly in Germany! Have your passport handy, but you won't need it. Railjet trains make it in just over an hour, and run every two hours, so avoid catching local trains that need a change at Rosenheim.
The fortress dates from 1205 and is reached by a funicular. One of the best things about the fortress is the pipe organ, which booms out from the tower each day at noon, and you can watch the organist at the foot of the fortress playing remotely in a small shed. The restaurant in the fortress is great with genuine local fare, like Gröstl and Schnitzel.
Also in the town are a distinctive City Hall, a fountain, two churches and the Old Town.
Halfway between Salzburg and Vienna, this is a good place to stop off at on your way between the two, or even for a night in itself. Remember our tip: it may be cheaper to buy a Salzburg-Vienna ticket, and just get off at Linz. There's no barriers to stop you doing this. Obviously you'd need a separate ticket for the rest of your journey, but it can work out a lot cheaper.
Next tip: the Hauptbahnhof is about 30 minutes walk from the town square, and there are lots of trams, but you need to get the right ticket! The Mini-Karte is €1.10 and good for 4 stops, but cunningly the town square is 5 stops from the station. Up to you how you want to risk this! A Midi-Karte will get you all across town, but is €2.20. The Maxi-Karte is €4.40 and lasts for 24 hours.
One more ticket fact ... to get a ride on the funicular (Pöstlingbergbahn), tram 50 leaving regularly from Hauptplatz (which has ticket machines), it's a further €6.20 return (the ticket is called Berg Und Tal), and Maxi-Karte is not valid. OK?
The funicular is amazing. Taking in gradients of up to 12%, it wanders through some pretty suburbs and cottages, until reaching Pöstlingberg at an altitude of 540 metres. There's a church, a cafe, an art gallery and incredible views.
Linz has set itself up as a centre of excellence for technology, and has some of the most modern museums and galleries in the world. There's the ARS Electronica Center on the north bank of the river, and the modern art gallery Lentos on the south bank. Further into town is the Nordico city museum. The Tooth Museum (yes, really) is in the Old Town Hall next to the Tourist Information.
One shopping tip: the chocolate shop Isabella Confiserie, at Landstrasse 33, has a great selection, and is a good place to buy the famous Linzer Torte.