I actually saw this happen to a couple celebrating 10 years together. He didn't tell her where she was going until their got their connection in London. Fabulous surprise, lovely and heart-warming.
Now WHERE? ( It has to be a weekend, she misses the kids)
The traditional 20th gift is china, so you could take her to China (Taiwan or Hong Kong would suffice) but kinda far for a weekend.
The gemstone is emerald, so maybe a quick weekend to the emerald isles?
BTW, just got back from a long weekend in Cairo for my 20th (was yesterday). Swiss goes direct from Zurich, it's under a 4 hour flight, so doable for a weekend. It's pretty cheap (can get a five star on the Nile for under 200chf/night) and it's warm!
I love Paris or Rome for a weekend trip. Book a suite in a top hotel (Crillon/Ritz in Paris and maybe Hotel De Russie in Rome...great spa). Then get pampered in the hotel and book a few great meals. Get a limo with a guide to show you the city's most romantic/memorable spots.
...or, choose a city that is a little more unknown. Budapest is an amazing city with great hotels, spas and food. Boscolo and Corinthia both have beautiful hotels. And it is easy to get to.
I guess the 3rd choice is a mountain top suite in a great hotel in CH/Aus where you can take a train and start with a nice bottle of Champagne. Again, make sure it has a spa and DON'T bring skis!
Have fun!
How about somewhere really tacky like Venice?
http://m.mandarinoriental.com/barcelona/
http://www.hotelescenter.es/casafuster/
and restaurants:
http://www.gruptravi.com/xalet/index.html
http://www.torredealtamar.com/main_en.html
If you like this option and you want some advice, just tell me :-)
One of my most romantic holidays was spent in Istanbul. I loved the vibe of the city, and the variety - nice hotels, great restaurants and leisure possibilities... and not too far away for a weekend.
http://www.wien.info/en?set_language=en
Special offer on Swiss airlines
Leaves from various "romantic" cities in Europe for overnight trips and definitely do-able for a weekend.
http://www.orient-express.com/web/vsoe/journeys.jsp
If you decide to do just Paris, there's nothing like the Four Seasons George V:
http://www.fourseasons.com/paris/
PS: congratulations!
For our fortieth we went hiking! Had a lovely lunch at a super restaurant - quite Swish - in our hiking kit! Brilliant. We were lucky though, we were able to eat outside, so our lack of formal dress didn't seem as out of place as it would have done in the dining room!
I wouldn't necessarily recommend you did this with your wife though. Each to his own.
The Therme Hotel in Vals is wonderful for a weekend too.