If nature is your thing, come to this eastern-most part of Poland for its exceptional primeval forest and wetlands: the Puszcza Bialowieska and Biebrza marshes survived the onslaught of time, civilization, and war to become the last remaining European site of such extensive (and now strictly protected) natural beauty. Also in this region, you can canoe on the smaller, deeper, cleaner lakes of the Suwalszczyzna (as opposed to the Mazury) which includes the deepest lake in Poland, the Hancza. Another water-based adventure can be had along the Augustow canal, an engineering feat intended to provide an alternative route to the sea but which fell slightly short.
If animals are your thing, these parks prove what a little motivation can do: among numerous other species, bison and tarpan now again roam these lands. Both species - extinct in the region - were reintroduced and now breed in the wild. For yet another example of human/animal cooperation, visit the nearby Arabian horse stud farm in Janow Podlaski, strong evidence yet that Poles still love their horses.
As for people, Podlasie still shows signs of its past cultural, ethnic, and religious diversity: you can still enjoy some Lithuanian company and culture in Punsk, or catch a glimpse of Moslem Tartars in Kruszyniany. Spiritually, you can revive yourself in a Camaldolese monastery in Wigry (which serves as a summer hotel), or explore the Baroque synagogue dating back to the 1600's in Tykocin.