Retiro Park (Parque del Buen Retiro)

125 hectares of green space that used to be reserved for royalty and is now the park where all of Madrid goes on Sunday. The lake (Estanque Grande) has rowing boats for EUR6 per 45 minutes, and the monument to Alfonso XII at its edge is where Sunday afternoon drummers gather and families spread out blankets on the steps. The Crystal Palace (Palacio de Cristal) is a 19th-century glass and iron conservatory that hosts free contemporary art exhibitions organized by the Reina Sofia. The building itself, reflecting in its pool with turtles swimming below, is more impressive than most of what's inside.

The rose garden (La Rosaleda) has 4,000 bushes and blooms spectacularly from May to June. The Fallen Angel statue (El Angel Caido, a depiction of Lucifer) sits at exactly 666 metres above sea level, which is either a coincidence or the greatest urban planning joke in history. The Paseo de las Estatuas is a tree-lined promenade with statues of Spanish monarchs that were originally made for the Royal Palace but considered too heavy for the roof.

The park is free, open daily from 6 AM, and is the reason Madrid is liveable in summer. When the temperature hits 38 degrees, the shaded paths and the lakeside breeze make the Retiro the only comfortable outdoor space in the city. Runners use the perimeter path (4.5 km loop) in the early morning. Yoga groups meet on the grass near the Crystal Palace. Puppet shows for children (Teatro de Titeres) run on weekends at noon near the Puerta de Alcala entrance.

Practical note: the park is large enough that you won't see everything in one visit. The lake and Crystal Palace are in the western half. The rose garden and Fallen Angel are in the south. The Velazquez Palace (more free art exhibitions) is in the northeast. Pick two or three areas and give them time rather than trying to cover everything.