Weird borders

Baarle-Hertog/Nassau

In 1843 this town was split between two countries on an almost house-by-house basis, resulting in at least 20 enclaves

Nahwa

The largest second-order international enclave, also the only one outside Baarle-Whatever

Vennbahn

A railway line that used to run through a country while being part of another country, now a bike path

Gornja Siga

A strip of land next to the Danube, claimed by neither of the surrounding countries, where someone attempted to create a micronation

Bir Tawil

The same but in Africa

Vélez de la Gomera

This very small (0,02 km²) rock in another country's coast was the cause of at least one international incident

Hans Island

The dispute over this island allegedly led to the "Whiskey war", where soldiers of either country would plant the flag and leave behind a bottle of booze.

Dhekelia

A road belonging to a certain country separates two sides of an island (one of which is also an unrecognized state)