Buy the red Multi card (€2.50, at any machine) and load a 10-ride pack (~€6–12 depending on zones) — it’s shareable between travellers on buses and single-zone rides. Rides run every 2–4 minutes, the network closes 01:30–06:00, and the airport adds a €3 supplement each way. Day-trippers should price the Tourist Travel Pass instead: zone T versions cover the whole region, sierra trains and interurban buses included.
Cercanías commuter rail is the visitor superpower: Sol and Atocha sit on a spine that reaches Alcalá de Henares in 35 minutes, Aranjuez in 45, El Escorial in an hour and Cercedilla’s mountain trailheads in 80 — with the little C-9 continuing to 1,830 m at Cotos. Same card family, turn-up-and-go, luggage-friendly. If your Madrid trip has a day trip in it (it should), it almost certainly runs on these rails.
Chamberí’s Andén 0 — the 1919 ghost station preserved with its tiled adverts — is free on weekends. Atocha’s tropical palm house makes waiting a pleasure. And the C-9’s Puerto de Navacerrada platform at 1,765 m is arguably the best “station” in Spain: step off into pine forest and ski air.
Curated picks are coming — meanwhile, the live search covers every bookable property at the same price or better.