The Zócalo

Under the paving is the ceremonial precinct of Tenochtitlan, the Mexica capital that stood on an island in a lake until 1521. The Spanish did not build beside it; they built on it, using its stone. The cathedral went up over the sacred precinct, the viceroy's palace over Moctezuma's, and the lake was drained over three centuries — which is why the whole centre is sinking, visibly, and why the cathedral's floor slopes.

Why it is called the Zócalo

In the 1840s a monument to independence was begun in the middle of the square and abandoned at the plinth — the zócalo. The plinth stayed for decades, the name stuck, and it spread: main squares all over Mexico are now called zócalos after a monument that was never built here.

The flag

A single enormous flag stands in the centre. Soldiers of the presidential guard raise it in the morning and take it down in the evening with a slow ceremony that stops traffic across the square; the exact times shift with the season and the calendar, so treat it as a morning-and-evening event rather than a scheduled show. It is the reason to be here at 08:00 rather than at noon.

Metropolitan Cathedral, north side. Built between 1573 and 1813, which is why it changes style as you look up. Free to enter the nave; the bell towers and the crypt are shown on guided visits arranged inside.

The cathedral publishes its schedule as images rather than as text on its own site, so we do not print visiting hours we could not read — the times are posted at the door and mass takes priority over sightseeing.

Palacio Nacional, east side, is still the president's working palace, which is why access changes without notice: the murals on the main staircase — Rivera's account of Mexican history from Tenochtitlan to the Revolution — are free with photo ID at the gate when the building is open to visitors. Ask before you queue; the palace page has what we know and what we do not.

The Templo Mayor, at the corner, is the Mexica great temple, uncovered after an electricity crew hit a monolith in 1978, with its own museum behind. It is the only paid entry on the square and the one that makes the other three make sense.

Work began in 1573 and finished in 1813, which is why the facade is Renaissance at the bottom, Baroque in the middle and Neoclassical at the top — you can read the change of taste vertically. Inside, the two great retablos behind the altar are the reason to walk to the far end: the Altar of the Kings, gilded and dense enough to be exhausting, and the Altar of Forgiveness in front of it. The organs above the nave are among the largest colonial instruments anywhere.

The floor slopes, and it is not your eyes. The whole centre stands on the drained bed of Lake Texcoco and has been sinking for four centuries; the cathedral has been shored, jacked and stabilised repeatedly, most seriously in the 1990s, and a plumb line hung from the dome inside shows the tilt. It is the most legible piece of evidence in the city that the ground here is not ground at all.

Entry to the nave is free. Guided visits to the bell towers and the crypt are arranged inside the building rather than online, and services take priority over sightseeing — the cathedral publishes its schedule as images on its own site rather than as text, so we do not print hours we could not read. What is reliable: mornings are calmer, and the north-side entrance is the one that is usually open.

08:00 is the quietest hour and the flag is going up. Midday is full of school groups, vendors and, most days, some kind of installation. Dusk is when the buildings are lit and the flag comes down. Sunday brings families and the biggest crowds, and it is also the day the INAH museums are free for nationals and residents, so the Templo Mayor is at its fullest.

Dates to know: the night of 15 September, when the president gives the Grito from the palace balcony to a packed square and the centre is closed off from the afternoon; 1 and 2 November, when the Day of the Dead installation and the parade route pass through; and December, when an ice rink and a Christmas market take the middle of it. The dates that change a trip has the rest.

The arcades on the west side hold the cheapest sit-down coffee with a view of the paving, and the terrace restaurants above them — reached through the hotels on that side — are the ones with the photograph everyone takes of the cathedral at dusk. Prices there are for the view rather than the food.

Walk two blocks and it changes: Calle 5 de Mayo and the streets towards Bellas Artes are lined with cantinas and taquerías, and the Mercado de San Juan, fifteen minutes west, is where the city's cooks buy. A food walk through the Centro is the shortcut if the menus are unfamiliar; where to eat has the named places with the guides that list them.

Metro Zócalo on Line 2 exits directly onto the square — the station is beneath it, and the flag is the first thing you see coming up the stairs. Metro fares are MX$5 a trip on the operator's published tariff. From Roma or Condesa an app car takes 15 to 30 minutes depending on the hour; from Coyoacán, 40 minutes and up.

Driving into the Centro is a mistake: much of it is pedestrianised, the rest is one-way, and parking is scarce and expensive.

Once you are here the whole Centro Histórico is walkable, and flat: Bellas Artes is twelve minutes west, the Templo Mayor is at the corner, and the Torre Latinoamericana viewpoint is on the way to the palace of fine arts. Getting around covers the rest of the network.

Lit up, the square is at its best: the cathedral floodlit, the palace facade in warm light, the flag down and the paving nearly empty by nine. The blocks immediately west, towards Bellas Artes, stay busy with cantinas and street food well past that. The blocks north and east do not: offices and wholesale streets that close at six and thin out fast.

The practical version: stay on the lit pedestrian streets — Madero, 5 de Mayo, Regina — take an app car rather than walking out of the Centro late, and treat the crowd around the metro exits the way you would any crowded station anywhere. Residents will name Tepito, a few blocks north-east, as the area to stay out of; it is not somewhere a visitor has any reason to be.

If you want the square at its emptiest rather than its liveliest, come back at eight in the morning instead. Between the flag going up and the first coach parties there is about an hour when four centuries of buildings stand around an almost empty rectangle, and it is the best photograph in the Centro.

Arrive at 08:00 for the flag and an empty square, do the cathedral, then the Templo Mayor when it opens at 09:00, and the Palacio Nacional murals after that. By midday you are ready to walk west to Bellas Artes for lunch and the mural floor. That is the morning half of the one-day itinerary and it costs one MX$210 ticket.

The rest of the city, and the order to take it in, is on the Mexico City city guide.