If you happen to between in Switzerland within a day or so to spare, you'll have happy to know that you can kill two birds – visiting a new country and getting out of Zurich for the day – with one stone: The tiny sovereign state of Liechtenstein.
With this being said, while the Liechtenstein country is located less than an hour from Switzerland's largest city by car, meaning that it has the potential to be one of the high points of a trip to Switzerland, reality might not line up with your expectations unless you calibrate them correctly. Liechtenstein is far from interesting, but it is certainly strange.
Things to Do in Liechtenstein
Considering the size of Liechtenstein (less than 62 square miles), the 10-minute drive up to Vaduz Castle is very long, to say nothing of the additional 10 minutes it takes to walk down to the castle from the parking area. Indeed, 20 minutes isn't a lot of time to spend, but it is a lot of time to waste: Make sure to time your visit right, or you might not be able to enter Vaduz Castle.
Seeing sights in the rest of the city/state/country exposes you to similar opportunities for disappointment, from a tourist perspective anyway, with little more to offer than a small menagerie of museums (including Liechtenstein National Museum and the Liechtenstein Museum of Modern Art, among a few others), a church and a pedestrian street where certain cars seem to drive as they please – watch out.
Nature-wise, there's not much within the tiny territory of Liechtenstein country that isn't populated, although the view from Vaduz Castle is rather scenic. If you have mountaineering equipment (or, more importantly, skills) you could technically scale some of the peaks the rise behind Vaduz's city center, although the Alpine scenery and activities within Switzerland-proper are superior no matter which way you look at it.
Why Does Liechtenstein Exist, Anyway?
Being in Liechtenstein might be disappointing or even downright boring, but the country seems a bit more interesting (or, at least, strange) when you understand a few things about.
On one hand, it isn't strange that there is no political boundary between Switzerland and Liechtenstein – both are part of the passport-free Schengen Area, which has existed on the European continent for as long as I've been traveling. There isn't any obvious geographical boundary, however, which coupled with the easy-to-miss road sign announcing your arrival into Liechtenstein country, makes you call the necessity of its very existence into question.
The answer, or at least one of them, seems ironic when you consider Switzerland's reputation as a tax haven for the wealthy. Tax rates are even lower in Liechtenstein, while incomes are higher and whose public services are both more extensive and more expensive. "You might say," tax-dodging Swiss businesspeople are known to say to one another in hushed conversation, "it's the Switzerland for the Swiss."
Additionally, there are historical reasons for the existence of Liechtenstein, although the weight of history might escape you as you try to shoo away sleep during your promenade through the town center of Vaduz. Perhaps dreaming of sojourns to other tiny European countries, such as San Marino, Andorra or Vatican City?
How to Reach Liechtenstein
Disclaimer: There are dozens of other (better) day trips to take if you find yourself in Zurich with nothing else to do, from the medieval citadel in Baden, Aargau, to the majestic Rheinfall waterfall, to the picturesque city of Lucerne, located in the foothills of the Alps, a city's that both dynamic and beautiful at the same time.
If you do still want to go to Liechtenstein – hey, it's another country to add to your list – it's rather simple. The easiest way to go is by car: It's about an hour from Zurich via the A3; you can also reach it from Munich or several cities in western Austria, although it's definitely not worth going that far out of your way. Alternatively, take a train from Zurich Hauptbahnhof to the cities of Buchs or Sargans, and connect from there via bus.
(If you have to go to more effort than this to visit Liechtenstein, its probably not worth it.)