Law /
Questions about gaining a Polish citizenship and the process of getting one. [29]
What is the Schengen Zone?
Schengen Zone are countries that do not have the border control (it can be reinstated though for short periods of time) - you can cross the borders anywhere you like. You can drive a car through Polish-German Polish-Czech Polish-Slovakian border and noone will stop you (normally) to check you pass and the like. Poland is a part of Schengen Zone and I guess all the rules of Schengen Zone for apply
check with American State Department on visa requirements for travel in the EU
Poland is a party to the Schengen agreement. As such, U.S. citizens may enter Poland for up to 90 days for tourist or business purposes without a visa. The passport should be valid for at least three months beyond the period of stay. For further details about travel into and within Schengen countries, please see our fact sheet. - This is a quote from the American Department of State
another quote:
Please note, that while business and tourism visits of less than 90 days to the Schengen countries are visa-free, if you are traveling to Europe for any other reason—employment, study, internship, etc., your host country may require a visa for that purpose, to be obtained before you leave the U.S. Please check with the Embassy or Consulate of the country(ies) you are going for their specific requirements.
Although European Union regulations require that non-EU visitors obtain a stamp in their passports upon initial entry to a Schengen country, many borders are not staffed with officers carrying out this function. If an American citizen wishes to ensure that his or her entry is properly documented, it may be necessary to request a stamp at an official point of entry. Under local law, travelers without a stamp in their passports may be questioned and asked to document the length of their stay in Schengen countries at the time of departure or at any other point during their visit, and could face possible fines or other repercussions if unable to do so.