1. Belgium and the Netherlands

Border: Baarle-Nassau and Baarle-Hertog enclaves
Area: Unknown
Est. Gross Domestic Product: $1.1 trillion (The Netherlands) / $627 billion (Belgium)*

The border puzzle of Baarle-Nassau and Baarle-Hertog is unlike any other, as the Netherlands and Belgium are entwined in a convoluted web of enclaves and exclaves. This unusual configuration, the result of property transactions and treaties dating back centuries, consists of about two dozen Belgian territorial parcels tucked away within the Dutch landscape.
Belgium and the Netherlands ©Jérôme/Wikimedia
The border, which distinguishes one country from the other with white crosses, is drawn through the town so precisely that it spans over streets and buildings. The peculiar delineation has peculiar effects on day-to-day existence: eateries can be legally renamed as other countries, and residences are classified as Dutch or Belgian according to where their front doors are located.