Stockholm is Europe's toughest city in which to score a moderately priced hotel room; average nightly rates come to €111 (about $146). That's according to a survey from the folks at Cheaphotels.org, an online agency that periodically publishes data on hotel costs. The rates listed represent average prices for the cheapest available double rooms at minimum two-star hotels from June to August 2012.

In my experience, the price spread between tourist-oriented two-star hotels and the more business-oriented four- and five-star hotels has become almost as wide as the spread between economy- and business-class airfares. Unlike economy class, however, two-star accommodations can be perfectly comfortable.

You shouldn't ever pick a destination just because of low-priced lodging. But many of the cheapest places to visit on this list are world-class destinations—so if you're planning a trip to Europe, put them on your radar.

Start the slideshow to see a list of the most expensive and most affordable cities in Europe, compiled by SmarterTravel editors.