Athens moves a vast population. The transport system serves more than four million inhabitants spread across the sprawling Attica basin, and it does so with an unusually full toolkit: a dense bus network, three metro lines, trams, suburban and national rail, ferries from its great port, and even a funicular climbing one of its hills. Coordinating much of it is OASA, the Athens urban transport organization, the umbrella under which the city's separate operators run. For a metropolis pressed between mountains and sea, with ancient streets too narrow to widen, layering transport above and below the surface has been less a luxury than a necessity.

The metro's roots run surprisingly deep. Line 1, the Green Line, traces its origin to 1869, making it one of the oldest urban rail lines in the world. For most of its 25.7-kilometer run from the port of Piraeus up to leafy Kifissia it travels at ground level, threading 24 stations through the city's spine. The underground Red and Blue lines came much later, built largely in the 1990s and opening in January 2000 in time for the new century. Together the three lines carry well over a million passengers on a typical day, the trains sliding beneath a city that, two decades before, had almost no subway at all.

Above ground, the network is just as varied. OSY runs the buses - a fleet of nearly 1,900 vehicles, formed in 2011 by merging the city's two older operators. Hundreds of them are electric trolleybuses, drawing power from overhead wires strung above the avenues, though each one carries a diesel engine in reserve in case the power fails. Out at the edges, intercity coaches fan across the mainland, and at Piraeus the system meets the water: ferries depart for the scattered islands of the Aegean, and cruise ships nose into one of the Mediterranean's busiest harbors. A single journey can begin underground beside an ancient grave and end on the deck of a boat bound for the islands.

The rhythm of Athenian transit keeps stretching later. A handful of bus lines - the 11 and the 040 among them, along with night routes and airport express services - have long run around the clock. In September 2025 the city went further, introducing 24-hour service on select bus and metro lines on Saturdays, hoping to keep residents and tourists moving through the small hours. The express buses from Athens International Airport, the X93, X95, X96 and X97, still run all day and night, each one threading toward a different corner of the capital. Slowly, a city famous for its ancient past is learning to stay awake all night in the present.