The Paseo de la Castellana is Madrid's spine, a dead-straight boulevard that runs north for kilometres and gathers up the city's monuments, money and ambitions as it goes. Walk it from the bottom up and you walk through two centuries of the capital deciding what it wanted to be.
Begin at Cibeles, the fountain and the wedding-cake post office turned city hall, then up to Colón with its outsize flag and its column to Columbus. The avenue proper starts here. A little north, the surprise: the Museo de Escultura al Aire Libre, a free sculpture museum hung under the Juan Bravo flyover, Chillida's steel 'Sirena' suspended from the bridge among the traffic noise. Most people walk straight past it; you shouldn't.
Step east to the Lázaro Galdiano mansion for a quieter half-hour, then back to the median and keep climbing as the office towers gather. The walk ends at Nuevos Ministerios, Zuazo's brick arcades, the towers of AZCA just beyond — and a metro that takes you anywhere.