Zócalo

Where it sits. Mexico City's main square is a bare rectangle of grey paving roughly 200 by 240 metres, set in the middle of the Centro Histórico at about 2,240 metres above sea level. Its formal name is Plaza de la Constitución; the nickname zócalo — plinth — stuck after a monument planned in the 1840s got no further than its base, which sat alone in the square for years. The Metropolitan Cathedral closes the north side, the National Palace runs the whole length of the east, the arcaded Portal de Mercaderes shelters hat sellers and jewellers to the west, and the old city government buildings hold the south. There are no trees, no fountains and no benches, and that emptiness is the point: the surface can absorb a hundred thousand demonstrators, an ice rink, a book fair or a film unit within a single day.

The ground underneath. The plaza covers part of the ceremonial precinct of Tenochtitlan. The Templo Mayor's excavated foundations begin at the north-east corner, uncovered after electricity workers struck the carved Coyolxauhqui monolith in February 1978 and an entire block of colonial buildings was cleared for archaeology. The whole district sits on the drained bed of Lake Texcoco, and the clay below is still compacting. The cathedral, begun in 1573 and only completed in 1813, sank so unevenly that engineers spent much of the 1990s under it, excavating shafts to bring it back toward level; the nave floor still visibly tilts. Across the square, the National Palace stands on the site of Moctezuma's Casas Nuevas and carries Diego Rivera's stairway murals of Mexican history, painted between 1929 and 1935.

On screen. The Zócalo's most-watched appearance is the opening of Spectre (2015). The unit shot the Day of the Dead sequence on 20 March 2015 with roughly 1,500 costumed extras whose make-up call began at 4:15am; the first usable take was not captured until early afternoon. The single-take opening starts inside the Gran Hotel Ciudad de México on the square's south-west corner — its 1908 stained-glass ceiling and open-cage lifts are the hotel Bond walks through — then follows him out across the plaza and onto the rooftops before a helicopter corkscrews above the crowd. The parade itself was invented for the film: Mexico City had no such procession. Its popularity created one. The city staged its first official Day of the Dead parade on 29 October 2016, and it has run annually since, drawing hundreds of thousands of people to the same paving stones.

What you actually see today. The rhythm of the square is set by the flag. Soldiers of the presidential guard march out each morning to raise an enormous national flag on the central mast and return at six in the evening to lower and fold it, a slow, choreographed ceremony worth timing a visit around. Around the edges, concheros in feathered headdresses dance to shell drums in clouds of copal smoke near the cathedral steps, scribes with typewriters work the arcades, and the Nacional Monte de Piedad — the national pawnshop, founded in 1775 — occupies the north-west corner. The Templo Mayor museum, designed by Pedro Ramírez Vázquez and opened in 1987, holds the Coyolxauhqui disc and the ten-tonne Tlaltecuhtli monolith found in 2006. Rooftop terraces at the Hotel Majestic and the Gran Hotel give the postcard view down onto the flag.

How the square is used. More than any other public space in the country, the Zócalo functions as a political instrument. Presidents deliver the grito de independencia from the National Palace balcony on the night of 15 September to a packed plaza. Teachers' unions, farmers and marchers from every state camp here to be seen. It has also hosted Spencer Tunick's mass nude photograph in 2007, free concerts by Rosalía, Grupo Firme and Café Tacvba, a temporary ice rink each December, and a monumental Day of the Dead ofrenda every autumn. Any given week the square may be fully open, half fenced for a stage build, or occupied by protest tents — worth checking before making a special trip.

Getting there and timing. Metro Line 2 stops directly beneath the plaza at Zócalo/Tenochtitlan station, whose platforms display a scale model of the Aztec precinct. Entry is free and the paving is flat and step-free, though the metro itself is not reliably accessible. Early morning gives the cleanest light on the cathedral's tezontle-red and limestone façade and the thinnest crowds; late afternoon light rakes across the National Palace. From the square, Calle Madero — pedestrianised in 2010 — runs 900 metres west past the tiled Casa de los Azulejos to the Palacio de Bellas Artes, with the 1956 Torre Latinoamericana alongside for the highest open-air view of the valley. Altitude is real here: allow a day before walking hard.