https://www.youtube.com/watch?v=r5qC21x-5AU
Sofia Bulgaria has a super-modern subway system
https://www.youtube.com/watch?v=6ofY6-VsU5c
Arsenalna (Арсена́льна) is a station on Kiev Metro's Sviatoshynsko-Brovarska Line. The station was opened in 1960 and is currently the deepest station in the world 105.5 metres.
https://www.youtube.com/watch?v=j4JVFNXUO8o
Melbourne metro
https://www.youtube.com/watch?v=YpAHcu43bFU&t=65s
A walk through Japan's deepest operational train station - Doai in Gunma Prefecture, on the JR Joetsu Line - and the surrounding area. There are 462 steps and 143 metres from ground level to the northbound platform (the southbound platform is above ground). There is no elevator or escalator.
https://www.youtube.com/watch?v=btw0DzDHliY
longest metro systems
https://www.youtube.com/watch?v=knwskfpyY70
