The Knežev Arsenal, or Rector's Arsenal, was once filled with the industrial sounds of cars and weapons being built. Now, when you enter the empty factory buildings and gritty courtyards, you're more likely to hear a rock concert or techno music and thousands of cheering fans.

Founded in the mid 1800s, the complex, also known as Military Technical Institute, was overseen by a French engineer. At the time, Serbia sought friendly relations with France, and to emulate the country's economic development. The facilities made the city of Kragujevac a center for weapons (starting with cannons), industry, and, later, automobiles. And while it has fallen into decay, the government has plans to preserve the site in recognition of its importance to the area and Serbia's industrial revolution. 

In the meantime, the ruins are a draw for people shooting music videos and TV shows, graffiti artists, and concert promoters. The site is best known for Arsenal Fest, a multi-stage music festival held annually each summer. (Although couples have been known to take wedding photos at Knežev Arsenal as well.) Every year, local authorities organize a clean up of the complex, but due to its lack of security, it quickly returns to the dirty condition that makes it beloved by people who appreciate ruins.