A trip to Kraków provides an excellent opportunity to visit the former Nazi concentration and extermination camps at Auschwitz (Oswiecim in Polish) and Birkenau. The camps lie about 80km (50 miles) to the west of the city and can be visited in an easy daytrip. Getting there is relatively straightforward. There are regular train and minibus services that make the journey in about 90 minutes. Additionally, several tourist agencies run coach tours; these usually include transportation from Kraków's main square and an English-language guide once you've arrived at the camps. If you're not completely up on your WWII history, this is one place where taking a guided tour makes sense to get the most out of the experience.
Getting there may be easy, but taking in the experience is anything but. Auschwitz-Birkenau was Nazi Germany's most notorious death camp and has come to be seen as a symbol of the Holocaust itself. The exhibits are in turn shocking and profoundly depressing. At the end of the day, as you're slogging through the immense open fields at Birkenau, where hundreds of thousands of Jews, as well as Poles, POWs, and political prisoners of many nationalities, were held before meeting their ends in gas chambers just yards away, you'll find yourself wallowing in a mix of despair and disgust. Kraków's colorful square, filled with people laughing over their coffees, seems a million miles away.
At the same time, there are powerful reasons for coming here, including bearing witness to this epic human tragedy. Alongside the exhibits of yards of human hair of the victims or empty canisters of Zyklon-B gas that was used as the killing agent, you'll also see rows and rows of photographs of those who died here and learn part of the story of where they came from, how they got here, and what they went through. It's no exaggeration to say this is likely to be the most moving experience you'll have in Poland, and the impressions you form here will last a lifetime. That said, Auschwitz is no place for children. If you're traveling with children younger than 14 or so, it's best to skip the camps altogether.