U-Bahnen, or underground trains, are a form of rapid transit found in many cities around the world. They operate primarily below ground, allowing for efficient transportation in urban areas. U-Bahnen systems typically consist of multiple lines that connect various neighborhoods, making it easier for residents and visitors to navigate the city. The first U-Bahn system was established in London in 1863, known as the London Underground. Today, cities like Berlin, New York, and Tokyo have extensive U-Bahn networks that serve millions of passengers daily, providing a reliable and fast alternative to road traffic.