Kotor, Montenegro 

Many of the city's best attractions are either completely free or almost free, including The Ladder of Kotor (a famous walking/hiking path) and the historic Kotor Maritime Museum, where admission is just over $4.50 per person. If you prefer a more laid-back activity, visit the secluded Bajova Kula Beach. (Pro tip: Enter on the right side for free admission; otherwise, you'll pay approx. $11 per person.) Durmitor National Park – another UNESCO World Heritage Site – is another highlight with its winding rivers, vast gorges, expansive forests, and scenic hiking trails. Entrance to the park costs just $3 – a total steal, especially compared to other national parks in Europe.