The proximity of Bratislava and Austria are much commented upon, at least locally. They are among the world's closest 'real' capital cities (if one excludes the Vatican City and Rome), though Kinshasa and Brazzaville actually pip them. But until recently, the physical links between them were fairly tenuous. The original road is relatively short but wends its way through a series of small towns and villages; there is now a motorway link.
The frontier, even after 1989, loomed large with unpredictable delays at the road border sometimes stretching to hours; Slovakia's accession to the Schengen agreement means that the border has effectively disappeared.
Boats occasionally stopped on their way between Budapest and Vienna, but many sailed straight past; there are now a regular services between Bratislava and Vienna.
In fact, for many years after the fall of the Iron Curtain Bratislava was often merely a tick-box one-day excursion ('Experience The Wilds Of Eastern Europe And Be Back For Supper!') for visitors to Vienna.
But things have changed. With its improved air links, Bratislava has carved out a niche for city-break visitors (not to mention 'stag' tourists). A significant number never go to Vienna.
The two places have a joint marketing effort as 'Twin Cities', cooperating most visibly through a regular Slovak / German /English magazine, and a fast river link, the Twin City Liner, which roars up and down the Danube several times a day between April and October.
And by rail or road the cities are just an hour apart (trains leave Bratislava's main station hourly).
But there are actually relatively few similarities between the cities. So if you find yourself at a loose end in Bratislava (or pretty much anywhere in western Slovakia) a day trip to Vienna can make for an amusing break from all things Slovak.
Arriving by train at Sudbahnhof, you emerge into one of Vienna's less glamorous districts to confront a six-lane road, with tram lines alongside: proof, if it were needed, that the city is on an altogether different scale from Bratislava.
Vienna’s Staatsoper opera house.
Photos by James Thomson
Getting to the historical centre (Stephansplatz) by public transport involves a fairly simple S-bahn/U-bahn dog-leg, but if the weather is fine a 30-minute stroll down quiet Argentinierstrasse will bring you to Karlsplatz, site of the monumental Karlskirche church. From Karlsplatz it is another 5 minutes to the even more monumental Staatsoper.
Between the buildings the soaring spire and multi-coloured tiled roof of St Stephen's Cathedral can be glimpsed. It's a wonderful building, though the number of visitors streaming in and around it can be a bit distracting.
If you want to avoid the crowds, continue towards the Donaukanal where, on the embankment is one of Vienna's oldest churches, St Ruprecht's. This small, eleventh-century Romanesque church is thought to be the oldest in Vienna and is, in its own modest way, as impressive as the Baroque monstrosities which litter the city. It is in the middle of the city's oldest district and the area around it, at least during the day, is mercifully quiet compared to the heaving masses of Stephansplatz.
A short walk away is the Museumsquartier, part of the Vienna Ring, along which Vienna's grandest edifices are to be found. Gigantic buildings fit for an empire, like the Natural History and, opposite, the Art History Museums, are almost ludicrously impressive.
But if art galleries and royal palaces are your thing you will want to stay for longer. Given an afternoon, you might instead want to take advantage of one the more offbeat attractions, which Bratislava lacks; for instance, a strudel-making exhibition, or the imperial furniture collection.
Also recommended is the Esperanto Museum, on Herrengasse, beyond the (it hardly needs saying) uber-grand Hofburg Palace. The museum has a range of materials in Esperanto as well as interactive displays on some even less successful made-up languages, from Voläpuk through Interlingua to Klingon.