From what I understand, it is legal for a US citizen to spend up to 90 days in Poland, leave for one day, and re-enter for another 90 day period. Sources I called the Polish embassy in New York and ...
What are the standard border checks when traveling between Warsaw and Berlin by various types of transit
I know that there is always a passport check when traveling by air. Is that the same case when traveling by train, bus, and car?