The tower's construction began in 2011, more than two decades after the land was procured.
The owner, Lotte Corporation, also oversaw the construction of the world's largest indoor theme park.
The structure is designed to hold up under a 9.0 magnitude earthquake.
It's also intended to withstand gusts of wind as strong as those seen in Hurricane Katrina (around 180 miles per hour).
At more than 1,800 square feet, it's the tallest building in South Korea and the fifth tallest building in the world.
The structure, which opened in in April 2017, has 123 floors and 42,000 windows. Construction of the roof alone required 3,000 tons of steel.
The design, though modern, was inspired by the curvature of traditional Korean art and architecture.
The facade consists of pale glass, a nod to Korean ceramics.
One hundred days after it opened, the tower had already attracted 10 million visitors, or around 120,000 people a day.
The building contains offices, retail outlets, and some of the most expensive apartments in Korea, which sell for around $1,825 per square foot.
It also features a luxury hotel called Signiel Seoul. The hotel's lowest floor still hovers above the city's second tallest tower.
Source: Korea Bizwire
The tower's standout features include a glass-bottomed observation deck and the world's fastest elevator.
The double-decker elevator, known as the Sky Shuttle, travels at more than 22 miles per hour. That means it can deliver people from the first floor to the observation deck on the 121st floor in a single minute.
The tower hosted a "sky run" in 2018, which challenged people to climb the 2,917 steps to the top.
Vertical marathons take place in other countries as well, but the Lotte World Tower's race is both the longest and the highest.
The tower could have a $3.8 billion economic impact.
The tower is also expected to receive around 60 million tourists a year — a goal that shouldn't be hard to achieve, now that it's been dubbed the best in the world.
Source: Lotte World Tower