North Korea watchers knew something was afoot as soon as cameras caught the train sliding into Beijing’s central station Monday night.

Twenty-one cars long and painted forest green with yellow piping, the train was ferrying Kim Jong Un to unannounced talks with Chinese President Xi Jinping. It marked the first time the North Korean leader has poked his head out from behind his borders on a state visit since taking power in December 2011.

But even before either government confirmed the confab was underway, experts and analysts suspected it. The train was a giveaway.

“The key detail does appear to be the train,” Adam Cathcart, an expert on Chinese-North Korean relations who teaches at the University of Leeds, told the Guardian this week. “If it were the foreign minister or Kim Yong Nam [North Korea’s nominal head of state] they would simply fly in from Pyongyang.”

North Korean leader Kim Jong Un, center, and his wife Ri Sol Ju, center right, are greeted by Chinese Communist Party members in Beijing station. (Korean Central News Agency/Korea News Service/AP)

But in 2018, what kind of world leader travels by train?

The answer is more complex than simple travel logistics. The Kim family’s fleet of trains — reportedly tricked out with five-star accommodations and cuisine — has long been a symbol of power in an indigent country where bad infrastructure is the norm and travel is restricted. The trains are the rolling inner sanctum of the secretive regime and have played a part in some of the country’s pivotal moments.

As The Washington Post’s Adam Taylor noted this week, Kim’s decision to ride the rails in China was pulled right from the playbook of his father, Kim Jong Il, and he made the trip on one of his father’s favored trains.

A special train is seen at Beijing Railway Station on March 27. (Kyodo News/AP)

The elder Kim, a notorious playboy, was also reported to be afraid of flying. During his reign, Kim Jong Il used six luxury trains for travel, the Associated Press reported in 2009. Based on U.S. and South Korean intelligence reports, South Korea’s Chosun Ilbo newspaper published a report that year on the leader’s private transportation. He had 90 armored carriages at his disposal. Twenty stations were built across the country for his use. When he traveled, three separate trains would run together in a caravan — a lead train to handle security checks and reconnaissance, the leader’s train, and a third containing his bodyguards and support personnel.

The trains featured “conference rooms, an audience chamber and bedrooms,” the report stated. “Satellite phone connections and flat screen TVs have been installed so that the North Korean leader can be briefed and issue orders.”

Video footage taken inside the train on a 2011 trip to China showed the North Korean leader holding meetings in a white-walled conference room and speaking with aides in a decorously carpeted sitting area. The accommodations were very James Bond-villain chic (Kim Jong Il was a big fan of the British spy movies, the New York Times reported after his 2011 death).

The armored vehicles were so heavy, the trains could move at only about 37 mph. Up above, the Kim family’s rail travels were often monitored by American U2 spy planes, the Chosun Ilbo reported.

“It had a reputation for being an opulent ride for the leader,” Curtis Melvin, an expert at the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies, told NBC News this week. “It maintains the North Korea leader’s lifestyle wherever he goes. It is capable of carrying the type of food and entertainment to support the leader as he travels.”

A rare inside peek at that on-the-rails opulence came in 2001, when a former Russian diplomat named Konstantin Pulikovsky published an account of traveling with the North Korean leader as the train lumbered across Russia for a visit to Moscow in the summer of 2001. According to the New York Times, the book described lavish meals consumed with silver chopsticks, karaoke and beautiful “lady conductors.” Fresh lobsters were shipped in for the journey, as were cases of Bordeaux wine straight from Paris.

“It was possible to order any dish of Russian, Chinese, Korean, Japanese and French cuisine,” he wrote, the Times reported. “Kim Jong Il can be called a gourmet.”

Pulikovsky added even Russian President Vladimir Putin’s rail transportation “did not have the comfort of Kim Jong Il’s train.”

Kim used the trains on many foreign visits, including eight trips into China, beginning in May 2000, The Post has reported.

The family’s use of luxury rail transport runs counter to train travel in their home country. As Andrei Lankov, a North Korea expert at Kookmin University in Seoul, noted for Radio Free Asia in 2016, North Korea, like many communist nations, sank most of its development dollars into building up industry. Infrastructure was historically ignored.

“North Korean railway technology has remained virtually unchanged since the 1930s,” Lankov wrote. “Until just a few years ago, one could frequently encounter a Japanese steam engine locomotive manufactured in the 1930s but still puffing along at a North Korean railway station.”

But the green and yellow trains remain an important symbol of the country’s regime and are a significant part of North Korean history. In December 2011, Kim Jong Il died of a heart attack — while riding his train, the BBC reported.

The fallen leader’s mausoleum in Pyongyang is stocked with lavish items from his reign, including luxury cars, a yacht and a life-size mock-up of one of the rail cars.

More from Morning Mix:

This high school rejected NRA ‘blood money’ for rifle team. Locals donated instead.

The horns were so loud they wrecked the violist’s hearing — and his career

‘The fatty on the train’: Kim Jong Un nicknames proliferate in China despite censors

Eric Trump: ‘Jeb! I love everything about my father.’