Hiking into Belarus
Belarus offers limited visa-free entry to the Belovezhskaya Pushcha National Park on its side of the border, when crossing by foot or bicycle at the border crossing point 4km south of Białowieża. Individual visitors must apply ahead of time by following the 'Visa Free' link at the National Park's website (https://npbp.by/eng).
The special-entry permit lasts for up to three days, and visitors using it are not allowed to travel further into Belarus without an appropriate visa. Using the website, visitors agree to a lengthy list of restrictions and rules, then indicate when they will arrive at the border crossing. Eventually a form is generated, which you print out and present with your passport at the border.
Given that nature doesn't recognise borders, this is an excellent way to fully explore the forest.