The Seoul city government unveiled a set of plans to transform an abandoned train maintenance depot in the central district of Yongsan into an international business district, with the construction of a 100-floor skyscraper and a sky trail linking high-rises there as the centerpiece.

In a press briefing Monday, Seoul Mayor Oh Se-hoon said the government will transform an area of unused land near Yongsan Station into an “international business district as a new center for global urban competitiveness and technological innovation.”

Under the plans, the Seoul city government will develop the roughly 500,000 square meters of land into the world's largest "vertical" city, with extensive green space.

“There has been no case of a development plan on this scale among the world's largest cities,” Oh stressed. The district will be about 4.4 times the size of Hudson Yards, New York's largest mixed-use development site, it said.

The district is scheduled to be built by 2030 so that businesses will begin to move into the futuristic urban space in the early 2030s. Construction will begin in the second half of 2025. The district will be reborn as a "Compact City" with urban areas that combine multiple functions such as work, leisure and housing within walking distance, according to Oh. The plan is part of a wider project to make the city more pedestrian-friendly, he said. Depending on the intended purposes, the district will be divided into three zones -- international business, business complex and business support, his office added.

The city aims to build a 100-story skyscraper, with the mayor saying it will become Seoul's landmark. To this end, the Seoul city government plans to allow a floor-area ratio of 1,700 percent -- the maximum ratio under the current law. The skyscraper will have amusement facilities on its top floor to attract tourists, such as observatories, and amusement rides.

The 45th floor of some buildings in the Yongsan business district will be connected to create a 1.1 km-long sky trail offering panoramic views of central Seoul. The basement floors of the district will host a concert hall, library, and art museum.

Furthermore, green areas including a large park will be provided as part of broader project aimed at making the capital more liveable. Under the plans, Yongsan Station will be connected to the Han River with pedestrian paths.

According to Oh, a total of 500,000 square meters of land will be covered with green space, with roads moved underground.

“The city government will secure green space not only in spaces (at ground level) but also in various spaces such as underground and raised areas covering subterranean roadways, to create a massive green space large enough to rival the entire business district,” Oh said.

For instance, a public park that covers some parts of Gangbyeonbuk-ro will be created, so that people can reach Hangang Park and Nodeul Island on foot. Currently, it is difficult to access those areas on foot because they are blocked by Gangbyeonbuk-ro.

Also, the district aims to become a zero-carbon district. “Using cutting-edge technologies, the district will become a zero-carbon district,” Oh said. “By introducing eco-friendly new transportation methods, we plan to gradually restrict the operation of diesel locomotives.”

"Seoul is an attractive city attracting many tourists from all over the world already, but it will be one of the top attractive cities," Oh said.

Earlier, he vowed to increase Seoul's standing on the Global Power City Index, a ranking conducted by the Japan-based Institute for Urban Strategies of major cities according to their "comprehensive power to attract people, capital, and enterprises from around the world."

Seoul was ranked seventh out of a total of 48 cities on the index's 2023 edition. Oh said he aimed to bring Seoul up to fifth place.

Once this reconstruction project is completed, it is expected to create 146,000 new jobs and induce annual production of 32.6 trillion won ($2.44 billion), according to city officials.