High Island Reservoir East Dam: Hong Kong's Most Accessible Volcanic Wonder

High Island Reservoir East Dam is the easiest place to see Hong Kong's world-famous hexagonal volcanic columns on land—but the most spectacular views of the Geopark's coastline are only visible from the sea. Located within the Hong Kong UNESCO Global Geopark, the East Dam offers visitors a close-up encounter with rhyolitic columns formed roughly 140 million years ago, some reaching up to 100 metres in height and 3 metres in diameter. For those who want to understand the full scale of this geological marvel, combining a land visit with a Splitdyboat Guided Hong Kong UNESCO Global Geopark Tour reveals a side of the East Dam that few travelers ever see.

Why the East Dam Matters

The East Dam is more than a scenic viewpoint. It sits at the edge of a supervolcano that erupted approximately 140 million years ago, leaving behind the world's largest coverage of hexagonal volcanic columns. Unlike the dark basalt columns found in places like the Giant's Causeway, Hong Kong's columns are made of pale, silica-rich rhyolite—a rarity globally. The columns here are preserved in remarkable condition, with some displaying S-shaped distortions caused by earthquakes and fault movements before the magma fully cooled.

Visitors to the East Dam can walk along the coastal trail, photograph the columns up close, and observe how wave action continues to shape the coastline. The site also features the anchor-shaped dolosse that protect the dam from wave energy, and Kwun Mun Sea Cave, the only sea cave visible after the reservoir's construction blocked the original channel.

 

How to Get There and How to See It

By Land: The East Dam Walking Tour

Splitdyboat offers a Geopark East Dam Walking Tour for travelers who prefer to stay on solid ground. This guided experience includes a live geological tour guide who goes beyond surface-level sightseeing—explaining the volcanic history, the formation of the hexagonal columns, and the stories behind the landscape. You are not just looking at rocks; you are learning why they exist and what they tell us about Hong Kong's deep past.

The walking tour covers the key features of the East Dam, including the hexagonal columns, the S-shaped distorted columns, the dolosse breakwater, and the sea cave. It is suitable for families and first-time visitors, and the terrain is relatively accessible compared to the more strenuous hikes in the area.

By Sea: The Best View of the East Dam

For the most dramatic perspective, however, the view from the water is unmatched. Splitdyboat's Hong Kong UNESCO Global Geopark Four Sea Arches Volcano Sightseeing Tour passes the High Island coastline by speedboat or yacht, giving passengers a sea-level view of the East Dam area and the columnar cliffs that frame it. From the boat, you can see the full extent of the volcanic formations—the columns that stretch along the coast and plunge into the sea, the sea caves and arches that are invisible from land, and the sheer scale of the Geopark's volcanic landscape.

The East Dam is included as a stop on the boat tour, allowing passengers to view the dam structure and the surrounding columns from a completely different angle. As Splitdyboat's own materials note, standing at the East Dam on land means you have not truly seen the Geopark—the most breathtaking scenery is on the water.

 

Practical Details for the Splitdyboat Tour

Tour: Geopark Four Sea Arches Volcano Sightseeing Tour (Speedboat Edition or Yacht Edition)
East Dam Viewing: Visible from the sea during the boat tour; guided land tour also available separately (Geopark East Dam Walking Tour)
Departure: Sai Kung Pier (meeting point: Sai Kung Seafood Street archway for speedboat)
Duration: 2 hours (speedboat) or 4–7 hours (yacht) for the boat tour; the walking tour is approximately 2.5 hours
Price: From HKD $480 per person (speedboat edition)
Suitable for: All ages on the yacht edition; speedboat edition is not recommended for pregnant women, people with back problems, or those prone to seasickness

What to bring: Hat, sunscreen, camera, water, comfortable clothes. For the walking tour, wear shoes with good grip—the coastal trail is exposed and can be slippery after rain.

Important note: The boat tour's route and the visibility of specific features depend on sea conditions. If a guided land experience at the East Dam is your priority, the dedicated walking tour with a geological guide is the better choice. For the most complete picture of the Geopark, consider doing both—land and sea offer entirely different perspectives on the same volcanic wonder.

 

Final Thoughts

High Island Reservoir East Dam is the gateway to Hong Kong's volcanic story, and it rewards visitors who take the time to understand what they are seeing. Whether you walk the coastal trail with a geological guide who can decode the landscape, or view the dam and its columns from the deck of a Splitdyboat tour, the experience is a reminder that Hong Kong's most extraordinary landscapes are not always where you expect them to be.