PAKisarazu, Chiba Prefecture
Umihotaru Expressway Rest Area
A rest area along the Tokyo Bay Aqua-Line, surrounded by sea in every direction, with 360° views. From the observation deck on the 5th floor, you can see Mount Fuji, Tokyo Skytree, ships and planes crossing the bay. You drive through a tunnel beneath the sea, then suddenly find yourself standing out in the middle of the bay. Come and experience that strange feeling for yourself.
Each season has a story from one of my visits.
SpringMarch
The day the setting sun met the summit of Mount Fuji
March 10, 2025. From Umihotaru, the sunset would line up exactly with Mount Fuji’s summit that day. I’d heard the sun would set near the summit on March 9 and 11 too, but if I was going to see it, I wanted the day it lined up perfectly. I left home early in the afternoon and drove through the Aqua-Line’s undersea tunnel.
I rested my arms on the observation deck railing and watched Mount Fuji across the water. The sun edged closer to the mountain, which looked as if it were floating on the sea. The chatter around me gradually faded, and before I knew it, I was holding my breath too.
The moment the sun touched the summit, light burst from the peak. A bright path stretched straight across the sea toward me. I had my phone ready to take a photo, but my fingers wouldn’t move. Only after the light was gone did I finally let out a long breath. I rearranged my plans for these few seconds, and I didn’t regret it for a moment.
SummerAugust
A midsummer night, slipping on a cardigan in the middle of the sea
It was a midsummer night. Wanting to escape the heat in Tokyo for a while, I got in the car without choosing a destination. The Aqua-Line tunnel beneath the sea is long and straight. I kept a steady speed and held the wheel lightly, feeling the evenly spaced tunnel lights slip past behind me. On roads like this, I can tell my driving is at its smoothest.
I parked at Umihotaru and started with a clam bun. Out on the observation deck, I split it open, and a briny aroma rose with the steam. As I took small bites of the hot bun, I realized the night breeze was cooler than I’d expected, so I slipped the cardigan I’d brought over my shoulders.
The bridge stretched away across the sea as a single line of light, while the city lights along the shore shimmered on the water. I’d been driving beneath the sea a little while ago, and now here I was in the middle of it, letting the night breeze wash over me. The change felt like stepping into a dream. Some nights, you just don’t want to go home, right? Maybe that’s why Umihotaru stays open 24 hours.
AutumnOctober
What’s that tower out there in the sunset?
One October evening, I stepped out onto the observation deck on the Kawasaki side. I’d heard people gather here to watch the sunset. I stood a little back from the railing, with my hands clasped behind me, and looked out to sea. In the middle of the bay, I spotted two striped towers standing like sails.
What could those things possibly be doing out there? They didn’t look like lighthouses, and unlike a ship, they weren’t moving. I looked it up and found that it was an artificial island called Kaze no Tō (Wind Tower), built to ventilate the undersea tunnel. So I’d just driven beneath it. I couldn’t believe that tower had been quietly refreshing the air under the sea the whole time.
As the sun sank, the tower slowly blended into the color of the sea. Before it disappeared, I quietly thought, “Thanks for that back there.” I doubt anyone thanks an island built to ventilate a tunnel. But once I knew what it was, I couldn’t just leave without saying anything.
WinterJanuary
I looked through the telescope—and snowy Mount Fuji was suddenly right there
A winter afternoon in January. On a clear, cold day, I figured I should be able to see a long way from Umihotaru. I zipped my navy down jacket all the way up and stepped out onto the observation deck. Across the water, Mount Fuji, capped with snow, looked tiny.
I peered through one of the deck’s telescopes, and the mountain that had looked so small suddenly filled my view. I could even make out the streaks of snow. I looked up at Fuji with the naked eye, then peered through the telescope again. Wait, that was the same mountain, wasn’t it? I caught myself pointing at it, even though there was no one beside me.
Turn the other way and a tall tower rises above a distant city. Mount Fuji, Tokyo, the sea, ships crossing the bay—on a clear winter day, you can take in all of Tokyo Bay from Umihotaru. I can’t wait to show someone. Next time, I’ll bring my friend along for a drive. I know she’ll say, “I get the telescope first,” so we’ll decide who goes first with rock, paper, scissors.
The story sections are fiction inspired by this location. For accurate information, please consult official tourism and information websites.
About this expressway rest area
Built on Kisarazu Artificial Island, a 650 m-long island surrounded by sea on all sides, this is a rare kind of rest area anywhere in the world. The island was created to connect the undersea tunnel to the bridge, and it was Japan’s first rest facility built out at sea. The Tokyo Bay Aqua-Line opened on 18 December 1997.
The 5-storey building was designed to resemble a luxury liner floating in Tokyo Bay. Floors 1 to 3 are car parks, and shops and restaurants are on floors 4 and 5. The observation deck on the 5th floor offers a 360° view of the sea.
On the Kawasaki side of the 1st floor, the actual cutter face of the shield machine used to bore the undersea tunnel is on display. It measures 14.14 m across. From Shiawase no Kane (the Bell of Happiness) on the Kisarazu side of the 4th floor, you can see Aqua Bridge and the sea on the Kisarazu side.
Things to enjoy here
Observation Deck
From the observation deck on the 5th floor, you can take in the view across Tokyo Bay, including Mount Fuji, Tokyo Skytree, planes and ships. Telescopes are dotted around the deck.
Sea-view Concourse
The free rest area on the 4th floor is surrounded by glass. Take a break while watching ships and planes pass by or the sun set.
Clam Dishes
You can enjoy all kinds of clam dishes here, including clam buns, clam curry, clam soba and salt-seasoned ramen with clams.
Location
The rest area is along the Tokyo Bay Aqua-Line and is accessible from both Kawasaki and Kisarazu. You can turn around at Umihotaru from either direction, so after your break you can head back the way you came. Local buses also run from Kawasaki Station and Kisarazu Station. For your GPS, enter Nakajima, Kisarazu City, Chiba Prefecture. Umihotaru is open 24 hours a day.
Nearby spots
More Roadside Stations & Rest Areas
How about one more stop along the way?
Maps & Sources
Official information sources
- Umihotaru (About the facility) (opens in a new tab)
- Umihotaru (Observation Deck) (opens in a new tab)
- Umihotaru (Sea-view Concourse) (opens in a new tab)
- Umihotaru (Diamond Fuji viewing notice) (opens in a new tab)
- Umihotaru (Shop and facility information) (opens in a new tab)
- Umihotaru (Access and fees) (opens in a new tab)
- Umihotaru (About the Tokyo Bay Aqua-Line) (opens in a new tab)
- Chiba Prefecture Official Tourism Website: Chiba Kankō Navi (Enjoy the Umihotaru Rest Area!) (opens in a new tab)