Beijing's subway system was impressive for its reliability - no signal faults here - and is now the biggest underground system in the world, while continuing to expand. (What was frustrating was the frequently long distances to change lines at most stations, which seemed inexplicable given the newness of the system.)
Beijing
April 2019
Location map not available
SM-G950F
F 1.7, 1/50 s, ISO 125, 4.2 mm