If World War III breaks out and nuclear warheads detonate in the sky, obliterating thousands if not millions of people, there will be people who will see the "Apocalypse" unfold before their very eyes in the comfort of their doomsday bunkers.

CNN reported on Tuesday that sales of luxurious doomsday bunkers have risen by as much as 700 percent since 2015. Moreover, overall sales have risen by 300 percent since Donald Trump won the U.S. presidential election last year.

A growing number of these "preppers"—the people purchasing units in these bunkers—hope to ride out various doomsday scenarios in luxury, according to The Atlantic.

Rising S Bunkers is one of several companies engaged in the business of building high-end shelters. Its presidential model unit reportedly includes a gym, a workshop, a rec room, a greenhouse, and a car depot.

Rising S reportedly offers plate steel bunkers, which can last for generations and store a minimum of one year's supply of food.

"While some want to bunker down alone, others prefer to ride out the Apocalypse in a community setting that offers an experience a bit closer to the real world," CNN reported.

Gary Lynch, Rising S's CEO, revealed that sales of the company's $500,000-plus units increased by 700 percent last year.

Without mentioning names, Lynch told The Atlantic that his clients include Hollywood actors and "highly recognizable sports stars."

Bunker builders said their customers are those who have expressed increased fear of a nuclear war breaking out or a national-debt default that leads to unrest. Others cited new fears like climate change, pandemics, terrorism, and far-left and far-right extremism.

The last time doomsday bunkers made headlines was in 2012, the year of the so-called "Mayan apocalypse" that was feared to trigger the end of the world on Dec. 21, 2012 based on some interpretations of the ancient Mayan calendar.

David Morrison, senior scientist at the NASA Astrobiology Institute, recalled that during those days he received numerous inquiries from people, some of them so afraid that they had begun thinking of killing themselves in advance, The Daily Mail reported.

Even after the "Mayan apocalypse" fears were proven to be unfounded, doomsday bunkers continued to rise.

In January 2013, a firearms manufacturing company called III Arms said it was building a fortified, self-sustaining community in Benewah County, Idaho.

Its "Citadel" project, as it was named, was aimed at people who share the company's views about "patriotism, pride in American exceptionalism, liberty as defined by the Founding Fathers, and preparedness to survive man-made or natural disasters," its website said.