Krakow, the old capital of Poland.

As the second largest city and former capital of Poland: 1. The city has very convenient public transportation. Trams and motor vehicles are completely separated, with trams running every few minutes, quickly and punctually. 2. The city is very safe, and you don't have to worry about security issues like you would in Italy or Spain. 3. The famous Wieliczka Salt Mine is located a dozen kilometers from the city and attracts 5 million tourists every year. The mine is 327 meters deep and 287 kilometers long, with nine layers. It was mined from the 13th century until 1996, a total of 700 years. The mine has rooms, churches, banquet halls, and underground lakes, like an underground city. Due to the complex terrain, visitors must be led by a guide and can only visit the three layers at depths of 64 meters, 90 meters, and 130 meters. The attraction offers explanations in seven languages. There are many people in line for English and Italian explanations, but unfortunately there are no Chinese explanations. 4. The most famous attraction is Krakow Central Square, which escaped the war and has completely preserved its medieval style. 5. The entire city is full of churches, each with its own characteristics. There are more than 20 churches in the city center, and Krakow has more than 300 churches in total. The locals are very devout. 6. Jagiellonian University, one of the oldest in the world, is located here. Copernicus and Madame Curie both studied here. The university has very beautiful buildings, especially the university's own church, which is worth visiting. 7. The Auschwitz concentration camp in the suburbs and Schindler's factory in the former Jewish quarter of the city have now been converted into museums and are highly recommended.