There's a regular bus service from Warszawa to Białowieża by Veolia (departure at 14:30 at PKS Warszawa Zachodnia, arrival in Bialowieża at 19:20).
internet site: bialowieza.gmina.pl/kategorie,59,61.htmlIf you like nature - Puszcza Bialowieska in Poland
Białowieża Primaeval Forest, known as Belaveskaya Pushcha (Белавеская пушча) or Belovezhskaya Pushcha in Belarus and Puszcza Białowieska in Poland, is an ancient woodland straddling the border between Belarus and Poland, located 70 km north of Brest. It is the only remaining part of the immense forest which once spread across the European Plain.
I went to Bialowieza a couple of years ago with my wife and I loved it. Magnificent place. We're going back again this year.