Migrants, blocked from going further into Europe, sit in a park in central Belgrade. Koca Sulejmanovic/EPA September 19, 2016 The hidden costs of closed borders for migrants stuck in Serbia Jelena Obradovic-Wochnik, Aston University and Mаrtа Stojić Mitrović, Serbian Academy of Arts and Sciences Blocked from crossing borders further into Europe, migrants are turning to smugglers.