Supraśl is only an example. there is so many nice spots

town in north-eastern Poland. It is the home of the Supraśl Lavra, one of only six Eastern Orthodox monasteries for males in Poland. Situated in the Podlaskie Voivodeship (since 1999). It is located in Białystok County, about 15 km northeast of Białystok. It is the seat of the Gmina of Supraśl. Its population numbers 4,526 (2004).
The Codex of Supraśl, the oldest Slavic literary work in Poland and one of the oldest of its kind in the world, is named after the Supraśl Lavra. As of September 20, 2007 it is on Unesco's Memory of the World list.

Wikipedia, compare also Polish version

 unique place worth seeing

my local time