Popocatepetl is the second-highest mountain in Mexico.

Popocatepetl is an active volcano located in central Mexico, in the states of Puebla, Morelos and Mexico. Its name is from the Nahuatl “Smoking Mountain”.

Popocatepetl is 43 miles southeast of Mexico City. Depending on air quality, sometimes it is visible from there, sometimes it’s not. Here’s a photo of a day on which it was visible:

What if this volcano had a serious eruption? There are 25 milion people living within a 62-mile radius of it.
A team of researchers from Mexico’s UNAM (the Autonomous University of Mexico), under the direction of Italian UNAM professor Marco Calo, has been studying Popocateptl and is on the verge of releasing a 3D image of its interior.

From the Associated Press: “In the predawn darkness, a team of scientists climbs the slope of Mexico’s Popocatépetl volcano, one of the world’s most active and whose eruption could affect millions of people. Its mission: figure out what is happening under the crater.”
“For five years, the group from Mexico’s National Autonomous has climbed the volcano with kilos of equipment, risked data loss due to bad weather or a volcanic explosion and used artificial intelligence to analyze the seismic data. Now, the team has created the first three-dimensional image of the whole 17,883-foot (5,452-meter) volcano’s interior, which tells them where the magma accumulates and will help them better understand its activity – and, eventually, help authorities better react to eruptions.”
“Marco Calò, professor in the UNAM’s Geophysics Institute’s vulcanology department and the project leader, invited The Associated Press to accompany the team on its most recent expedition, the last before its research on the volcano will be published.”
That’s the plan. You can see the article here.