Instead, they adapted the facade of a house across the street for the exterior scenes on Tepeji Street. They adapted a second location for the rooftop shots. And for the patio and interior views, they took another house, which was slated for demolition, and essentially remodeled it to replicate Cuarón’s family home, with attention paid to the smallest details: They hired an artisan to make reproductions of the original tiles, using techniques from the early 20th century.

I asked Cuarón why he had been so obsessive in recreating every last detail of even his house, when very few people would have known the difference. He replied flatly: “I would know.”

Mexico City, he said, is a place in constant tension between what it is and what it was.

“For me, it’s a place filled with past,” he said wistfully.

A cleaning woman was sweeping the street and sidewalk in front of the house next to his childhood home, the bristles of her broom scraping the concrete. “That’s another sound,” Cuarón said excitedly. “We have it in the film.”

Then the woman took a pail of water and started splashing the sidewalk and the facade of the house.

“That sound!” he exclaimed, his eyes lighting up. The film opens with Cleo scrubbing the family’s driveway using water and a broom, and Cuarón seemed pleased — perhaps even reassured — by this intersection of life imitating art imitating life.

For all that had changed, there were at least some things that remained as he remembered them.