Ostrów Tumski is the oldest part of the city of Wrocław.
It was formerly an island (ostrów in Old Polish) known as the Cathedral Island between the branches of the Oder River, featuring the Wrocław Cathedral built originally in the mid 10th century. The 13th century Main Market Square (Rynek) prominently displays the Old Town Hall.
In the north-west corner of the market square there is the St.Elisabeth's Church (Bazylika Św. Elżbiety) with its 91,46 m tower, which has an observation deck (75 m). North of the church are the Shambles with Monument of Remembrance of Animals for Slaughter (pl). Salt Square (now a flower market) is located at the south-western corner of the market square. Close to the square, between Szewska and Łaciarska streets, there is the St. Mary Magdalene Church (Kościół Św. Marii Magdaleny) established in the 13th century. Źródło: https://en.wikipedia.org/wiki/Wroc%C5%82aw
Worthy of note are certainly places like Tatry and Owl Mountains.
The hilly places in Poland is indeed much, much more - should go well in the Holy Cross Mountains and Pieniny.
The fact that in Poland there are many national parks are the best proof of how special this place is.
The Tatra Mountains, Tatras or Tatra (Tatry either in Slovak (pronounced ?tatri) or in Polish (pronounced ?tatr?)- plurale tantum), are a mountain range that form a natural border between Slovakia and Poland. They are the highest mountain range in the Carpathian Mountains. The Tatras should be distinguished from the Low Tatras (Slovak: Nízke Tatry) which are located south of the Tatra Mountains in Slovakia. The Tatra Mountains occupy an area of 785 square kilometres (303 sq mi), of which about 610 square kilometres (236 sq mi) (77.7%) lie within Slovakia and about 175 square kilometres (68 sq mi) (22.3%) on the territory of Poland. The highest peak, called Gerlach, at 2,655 m (8710 ft) is located north of Poprad.The highest point in Poland, Rysy, at 2,499 m (8200 ft) is located south of Zakopane.Źródło: https://en.wikipedia.org/wiki/Tatra_Mountains.