@ Reticent, so do you have suggestions for eye-opening wow places to visit in Europe? My sister and I will be starting starting east and working our way west to England.
A good start point would be Russia. The Western part of Russia, particularly St.Petersburg, is Europen, and has some of the most fascinating museums and architecture in the entire world. I would pick as my first spot the Maarinsky Theater, which houses the great Maarinsky Ballet and the Orchestra. Next would be the Hermitage Museums; they have the old and the new buildings. Be prepared to see the most amazing collection of paintings, sculptures and antiques -- and by the time you and your sis are done touring these two places, you'll both have run out of superlatives to describe what you saw there.
A digression... I find it odd that a country that produced the highly cultured Alexander III, Peter the Great, and Catherine the Great (ok, I know she was Prussian), also produced the thuggish and coarse Putin.
Onward to Prague, a beautiful city on a par with Paris in its architecture and museums. And the Czechs produce great beer.
Austria, the land of Mozart and many other classical musicians of note would be the next stop. If you have a chance go to Salzburg, where he was born and resided as a child and visit the Mozart Museum. If not you can opt for the Mozarthaus in Vienna.
La Scala in Milan comes highly recommended. Two of the greatest classical music conductors in history, Riccardo Muti and the lamented Claudio Abbado, plied their trade there, so why not pay homage to the great ones at their temples.
To Catalan. Check Barcelona and the surroundings in general, and if you still crave architecture, you'll find the works of Antoni Gaudi in the Modernist style intriguing. If you guys are foodie-types, you'll love the cuisine.
On to France. Paris is Paris with the usual, but if you like different... the Catacombs will be one for the memories. Next hop onto the train and head south to Aix-en Provence and the Luberon region, quaint and charming, and my favorite part of France. Food is religion down there.
If the Channel Tunnel folks aren't on strike, try that mode of transport, so that you can check it off your bucket list. Hopefully you don't restrict yourselves to England but add Scotland to your itinerary. In London, I never get enough of the impressive Victoria and Albert Museum, which houses the works of the Arts and Crafts Movement. Then head north to Scotland and Glasgow and absorb the works of the great Mackintosh and others at the Kelvingrove Art Gallery and Museum. And, finally, don't forget to eat and finish your haggis.
Enjoy.