Željava Airbase (Object 505)

Code-named "Object 505", this base was designed to withstand a 20-kiloton nuclear blast. It had its own power plant, water supply, and could house 1000 people in isolation for 30 days.

The base gained global fame after the 2016 documentary "Houston, We Have a Problem!", exploring the myth of a Yugoslav space program allegedly sold to the USA. While the truth is debated, the mystery adds to the allure.

Destroyed in 1992, the base is now a massive ruin. The runways are still visible, and the cavernous tunnels attract adventurers from all over the world. Outside sits a derelict Douglas C-47 "Dakota" plane—perfect for a historic selfie.