You'd have to have a heart of stone not to be moved by the little streets of Paris, the palaces of Vienna, or the twisting canals of Venice. After all, there's a reason these iconic cities are as timeless and as popular as they are. But Europe is more than just these well-known destinations. In fact, some of Europe's most beautiful and exciting cities are often also some of the continent's smallest or most unassuming.

"Europe is such a great place to visit to enjoy the varying cultures, food, and history," Sofia Markovich, a Travel + Leisure A-List travel advisor specializing in European travel, tells T+L. "It is easy to get around Europe, but the key to taking advantage of the diversity is to pick a region and travel throughout that area."

As Markovich suggests, it's a good idea to plot out your stay by region — think Western, Eastern, or Southern Europe. Markovich says this will "allow a traveler an opportunity to visit several countries on one trip," or at the very least, experience some of the continent's best cities in one go.

To maximize your next European vacation's day trip potential, Markovich also suggests narrowing down your home base to a major city where public transportation is a mainstay.

"Choosing larger cities as a hub provides the most flexibility and easy access to surrounding areas," she says. "For example, Munich is a great spot to stay in order to have easy access to Austria in addition to many must-see areas of Bavaria. Staying in a large hub opens the opportunity for many out-of-town tours and easy transportation options without having to spend countless hours traveling back and forth."

Indeed, Europe is incredibly easy to get around thanks to its various modes of transport, from bus to ferry, and of course, by hopping aboard its famed trains, which whizz you from one glamorous city to the next in mere hours.

For example, while visiting London, visitors can make their way to the medieval city of Bruges via a three-hour ride with Eurostar. Similarly, Poland's Szczecin is a beloved waterfront city that's just a quick, two-hour train trip from Berlin. Bratislava, the charming capital of Slovakia, isn't as popular a destination as Vienna, but it's an easy day trip from the famous Austrian metropolis (only an hour away by train) and is a perfect home base for wine-tasting expeditions in the surrounding countryside.

All of the European detours listed here are easy, convenient trips, with no private drivers or even car rentals necessary. But, perhaps more importantly, all of the cities included — few of which get the attention they deserve — offer intrepid travelers the chance to have a unique, under-the-radar European experience. Below, find 13 spectacular European second cities that are absolutely worth the day trip during your stay.