The capital of Baja is also home to the largest "Chinatown" in all of Mexico -- a fact that may surprise not a few people in the country and even abroad.

"La Chinesca," another name for the settlement, was home to hundreds of Chinese immigrants in the early 1900s and is found entirely under the ground. It consists of a maze of tunnels that connect with each other under Mexicali, Mexico.

The Chinese immigrants arrived south of California's Calexico in the early 20th century, all of which were laborers imported by the United States from China in the late 1800s to build train tracks, as per The Los Angeles Times. They later shifted to working in the cotton fields in the area, with some later leaving agricultural work to open up shops and cafes.

However, the Chinese experienced racism from the second Mexican Revolution and also some resentment from the locals due to the cheap labor they were known for. As such, they opted to make their homes underground. It also helped them escape the desert heat, according to Fox News Latino.

As the settlement grew, the subterranean "Chinatown" later harbored opium dens and brothels, even breaching the U.S. border underneath the ground.

Some archivists have speculated that the tunnels were also used to supply alcohol from Mexico to the U.S.

Today, the Chinese in Mexicali no longer occupy the underground settlement. The abandoned catacombs have since been made available for tours by the Committee for the Historic Center of Mexicali and Project Origins.

Some who have visited the underground community have since written about their experience, like W. Scott Koenig.

"One basement we visited staged what one of those 'dens of iniquity' might have looked like," he said of one of the cells in his piece for SanDiegoRed.com. "There's a daybed for the lethargic opium smoker with a nightstand containing several long-stemmed pipes."

Still roulette wheels and empty card tables sit, recalling jollier times in the now dark room's perimeter. Since the opiate-inclined came here to 'chase the dragon,' there are a couple of the swirling mythological creatures painted on the wall for good measure," he added.

He also explained that the Chinese settlers in Mexicali left their underground residence partly after air conditioning was invented. However, some Chinese families appear to still have a yen for underground living as there are apartment buildings that have been built to sit partially beneath the ground.

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