Poland (Polish: Polska ?p?lska ( listen)), officially the Republic of Poland (Polish: Rzeczpospolita Polska,a About this sound listen (help?info)), is a country in Central Europe,11 bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine and Belarus to the east; and the Baltic Sea, Kaliningrad Oblast (a Russian exclave) and Lithuania to the north. The total area of Poland is 312,679 square kilometres (120,726 sq mi),9 making it the 71st largest country in the world and the 9th largest in Europe. With a population of over 38.5 million people,9 Poland is the 34th most populous country in the world,12 the 8th most populous country in Europe and the sixth most populous member of the European Union, as well as the most populous post-communist member of the European Union. Poland is a unitary state divided into 16 administrative subdivisions. Źródło: https://en.wikipedia.org/wiki/Poland
The hilly places in Poland is indeed much, much more - should go well in the Holy Cross Mountains and Pieniny.
In Poland we will also find areas where there is a completely different vegetation and animals.You can mention here for example, Roztocze National Park and around the seaside.
The fact that in Poland there are many national parks are the best proof of how special this place is.