I've known about enclaves for a while. Landlocked territories that belong to one country but located in another, making for some rather interesting jaggedy border lines, and the potential for quick and comical country hopping. 

Today I learned about Baarle-Nassau (Netherlands) and Baarle-Hertog (Belgium), which is apparently one of the more complex examples. 

The map below shoes you which parts belong to which countries. 

You can reads more about this here https://en.wikipedia.org/wiki/Baarle-Nassau

There are also, rather bizarrely, enclaves within enclaves within enclaves, which are territories belonging to one country, surrounded by territories belonging to another country, which are then entirely surrounded by territories belonging to a third country. 

Nahwa is an example of this.

There is nothing more powerful in this world than words.

Taken from the wiki: Nahwa is a territory that forms part of the Emirate of Sharjah in the United Arab Emirates. It is a counter-enclave (or second-order enclave) within the Omani territory of Madha, which is itself an exclave of Oman and an enclave within the United Arab Emirates.

Crazy, huh?!