The Moscow Metro is a metro system serving the Russian capital of Moscow as well as the neighbouring cities of Krasnogorsk, Reutov, Lyubertsy and Kotelniki in Moscow Oblast. Opened in 1935 with one 11-kilometre (6.8 mi) line and 13 stations, it was the first underground railway system in the Soviet Union. As of 2023, the Moscow Metro, excluding the Moscow Central Circle, the Moscow Central Diameters and the Moscow Monorail, had 263 stations (300 with Moscow Central Circle and the Monorail) and its route length was 449.1 km (279.1 mi) (without Moscow Central Circle and the Monorail), making it the 10th-longest in the world and the longest outside China. It is the third metro system in the world (after Madrid and Beijing), which has two ring lines. The system is mostly underground, with the deepest section 84 metres (276 ft) underground at the Park Pobedy station, one of the world's deepest underground stations. It is the busiest metro system in Europe, the busiest in the world outside Asia, and is considered a tourist attraction in itself.The Moscow Metro is a world leader in the frequency of train traffic—intervals during peak hours do not exceed 90 seconds. The Moscow Metro is also the first and only one in the world to switch to this schedule. In February 2023, Moscow was the first in the world to reduce the intervals of metro trains to 80 seconds. Source: Wikipedia (en)