Moscow's first metro line was opened in May 1935, with 13 stations between Sokolniki and Park Kultury. This line was named the 'Kirovsko-Frunzensky Diameter' and given a red colour. Two more lines were added shortly after – the 'Gorky-Zamoskvoretskaya Liniya' (green line) and 'Arbatsko-Pokrovskaya Liniya' (blue line).