Tokyo Bay's Hidden Hiking Oasis Built on a Landfill

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At the end of March, an approximately 40-meter-high artificial hill in Tokyo Bay officially opened to the public. When people think of hiking in Tokyo, the mountainous Tama region — with popular spots like Mount Takao and Mount Kumotori — usually comes to mind.

But now, a new option offers a lighter, more accessible outdoor experience. This urban "mountain," visible from places like Odaiba and Tokyo Big Sight, introduces a refreshing green space in the heart of the city.

As a reporter with a passion for the outdoors, I was eager to visit the new hill at Umi-no-Mori Park (Sea Forest Park). For years, I had noticed the lush green forest from the Tokyo waterfront. I always wondered when the site — clearly under development, with visible land work and construction vehicles — would finally open.

A Quiet Entrance and Welcoming Nature

On a clear April holiday, I set out from the Odaiba area on my motorbike. There were no signs pointing to the park, but I had a general sense of the direction. My route was interrupted by a waterway at Akatsuki Pier Park, which forced me to backtrack. After passing through an undersea tunnel, I spotted a sign for the Sea Forest Waterway and soon arrived at the park.

*From the central entrance, stairs extend straight up to the summit. (©Sankei by Shigeki Harada)*

Because the park had just opened, parking was hassle-free. On holidays, the fee is ¥1,000 (about $7 USD) per car. To my delight, motorcycles parked for free.

I made my way to the summit by climbing stairs that cut through the trees. Many of the trees had small birdhouses, apparently crafted by children. That day, I saw crows and black kites. According to park materials, other species like shrikes and skylarks also inhabit the area.

From Landfill to Forest

Remarkably, this tranquil space was once known as "Trash Hill." It was created from 12.3 million tons of waste and construction debris deposited between 1973 and 1987.

In 2005, then-Governor Shintaro Ishihara announced a vision to transform the site into a green sanctuary for people, plants, and animals.

Later, the area hosted the cross-country segment of the equestrian competition during the 2020 Tokyo Olympics. It became one of the event's lasting legacy sites — a symbol of renewal shaped from the burdens of the past.

An Imperial Connection

Covering about 60 hectares, Sea Forest Park is larger than both Yoyogi Park (approximately 54 hectares) and Ueno Park. Around 240,000 trees from about 50 species have been planted. These include Japanese beech, Japanese bay tree, Japanese black pine, Oshima cherry, camellia, and mulberry.

The saplings were grown through collaboration between local residents and private companies. The park also features ponds and grasslands, designed to support a diverse and thriving ecosystem.

During the 1996 National Tree Planting Festival, Emperor Emeritus Akihito and Empress Emerita Michiko (then Emperor and Empress) planted trees here. At the 2018 National Tree Growing Festival, Emperor Naruhito and Empress Masako (then Crown Prince and Princess) returned to care for those trees. This further connected the space to Japan's natural and cultural heritage.

While tents and campfires are not permitted, visitors can enjoy picnics at designated tables and chairs in open plazas. Ball games and kite flying are welcome. Despite its size, the park remains uncrowded, offering a rare sense of openness not often found in central Tokyo.

*A small gorge has also been created. (©Sankei photo by Shigeki Harada)*

Two Peaks in the Bay

The park features two small peaks — West Hill and East Hill — each rising 42 meters above ground level. Built according to Arakawa River flood standards (roughly 41 meters above sea level), these artificial hills are higher than Tokyo's tallest natural peak in the city center, Atago-yama (26 meters in Minato Ward). They are slightly shorter than Shinjuku's artificial Hakone-yama (about 45 meters).

The summits offer panoramic views of Shinagawa, Shinkiba, and even the Boso Peninsula on clear days. The light trails throughout the park allow for easy hiking or jogging. Many follow the same slopes used during the Olympic equestrian events.

Sea Forest Park is perfect for a laid-back day outdoors. Bringing your own food and drinks is encouraged, and the open space makes it an ideal place to unwind.

Getting There

Access to the park is currently car-centric. Shuttle buses run from Tokyo Teleport Station (Rinkai Line) and JR Shinkiba Station, though with limited capacity. A pier at the site is also used during large events. The Tokyo Metropolitan Marine Park Division is considering introducing regular boat services depending on future demand.

Author: Shigeki Harada, The Sankei Shimbun

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