The most dangerous gangs in the world operate on an international scale, committing murder, producing and trafficking drugs, extorting local businesses, bribing and blackmailing politicians, running prostitution and illegal gambling operations, engaging in human trafficking, illegally dumping waste, and even running major corporations and legitimate businesses. Some of these gangs bring in as much revenue as Fortune 500 corporations and have the same level of sophistication to match. Where they differ is the ruthless violence and intimidation tactics with which they carry out their empire building.

No one can truly predict where danger might be lurking and waiting to attack innocent passersby. Even a farm in an isolated place might be harboring unknown perils underneath its seemingly harmless surface. Yet, there are also cities in the world where you just know that danger is constantly on the prowl. These cities are teeming with threats and menaces that anyone would not want to face. So which cities are these?

Great Wall of China seen from satellite (Photo credit: Wikipedia) Like the Great Pyramids of Giza, the Great Wall of China is an instantly recognizable landmark. In fact under perfect visual conditions and at a distance of 160 kilometers from the Earth the Great Wall is visible from low orbit. However not everyone knows how such a massive structure came into being. Who built the Great Wall of China? When?