Madrileños mark the first warm afternoons of April by sitting down. The edges of the Retiro's great lake fill with people facing the sun, and the rowing boats go out beneath the colonnade of the Alfonso XII monument. It is an example we might follow, because this is the month to see Madrid at walking pace. The mornings are still cool, with lows around 8°C, but the afternoons reach the high teens, the light lasts into the evening, and the heat that empties the streets after lunch in summer is still weeks away. Showers come on about ten days, so carry a light jacket and let one send you into a museum.
UNESCO inscribed the park and the Paseo del Prado together, as the Landscape of Light, and they are best taken the same way, as one long walk with no fixed timetable. The Paseo was remodelled under Charles III as the Salón del Prado, a promenade for the city to stroll along and be seen on, and Ventura Rodríguez's fountains of Cibeles and Neptune still mark its course. Start at Cibeles and walk south under the trees, past the Prado itself, to the Real Jardín Botánico by Atocha. Its tulip beds are at their best in early and mid-April in most years. On a weekday morning, soon after the gates open, there may be whole beds with nobody in front of them but a gardener.
Holy Week falls in March or April, depending on Easter, and Madrid keeps it more soberly than Andalusia does. The processions move through the old streets around the Puerta del Sol to military bands and long stretches of silence. The largest, Jesús de Medinaceli on Good Friday evening, draws tens of thousands of people. If your visit coincides, stay central and let the processions find you.
From the Botánico, cross the Paseo into the Barrio de las Letras, the sloping grid of streets where Cervantes, Lope de Vega, Quevedo and Góngora all lived during Spain's Golden Age. Lope's house on Calle Cervantes is a museum now, down to the small garden he counted among his comforts. Cervantes lies one street over, in the Trinitarian convent on Calle Lope de Vega. The two men were rivals who traded insults in verse, and each ended up at an address named after the other.