Road Trip Diaries #1: Umi Hotaru

In the middle of Tokyo Bay, there sits a handsome, white, 5-story structure remarkable as much for its awkward location as it is for its raw engineering. The artificial island stands there, surrounded by ocean, an unexpected accompaniment to the fishing boats and cargo ships which normally cruise around the bay.

Welcome to Umi Hotaru (海ほたる, Sea Firefly), a rest stop and parking area on the Tokyo Aqua Line expressway which links Kawasaki with Kisarazu in Chiba prefecture. Completed in 1997, the Aqua Line runs about 15 km across the bay, partially as a tunnel under the bay and partially as an elevated expressway. Umi Hotaru is located where the road transitions from underground to above ground. About 25,000 vehicles use the road daily.

The Aqua Line was created to reduce the drive from Kanagawa to Chiba, two critical industrial regions in the Kanto area. Before the tunnel was completed, the only option was to go around the bay and through Tokyo, which made for a trip of 100 km, taking up to 2 hours, but the Aqua Line cut that travel time to about 15 minutes.

While Umi Hotaru is, at its most basic, a rest stop on Aqua Line forming part of National Road 409, the island in the bay has quite few attractions and is a day trip destination in itself.

The first three stories of Umi Hotaru are for parking, and there is room for about 500 cars and trucks. The main attraction, of course, is on the 5th floor deck where visitors are treated to a panorama of view of the bay. On clear days, one can see both the skyline of Tokyo and the industrial coast of Chiba. Umi Hotaru sits very close to the approach path to Haneda airport, so if conditions are right, you can see approaching aircraft coming in for landing.
There 5th floor also boasts “Marine Court”, a food court which offers hamburgers, ramen and other fast food fare. Although you certainly won’t write home about the food, it isn’t bad and the prices are reasonable.
If a full meal isn’t your liking, head on down to the 4th floor. Here, you would find a Starbucks and Family Mart, along with a shopping arcade where you can pick up various tourist trinkets such as keychains, postcards and other items. There is also, perhaps unsurprisingly, a sushi restaurant on the 4th floor.
The radio stations Bay FM and Inter FM also broadcast from a studio on the island.
If you go down to the 3rd floor parking lot and walk across to the Chiba side of Umi Hotaru, you will find a small pavilion called Umi Megane (海めがね, Sea Glasses). This is a small building setup with exhibits which give visitors a glimpse at the mechanisms and methods used to construct the Aqua Line and Umi Hotaru were built, and they truly are engineering marvels.
Because the underground sediment was so soft in the location where the Aqua Line was built, engineers first had to bring in rock and other hard dirt from other areas of the country, and compact them down where the tunnel, bridge and island were going to be built. Construction on the Aqua Line began in 1980 and took 17 years to complete.

Umi Hotaru and the Aqua Line comprise part of National Road 409. From Tokyo, you can head toward Haneda Airport on Wangan Road （湾岸線） and get on the Aqua Line at Ukejima （浮島） Junction. The tunnel portion of the Aqua Line is a little over 9 km long, and you will see Umi Hotaru just as the tunnel comes up from the ocean.
Once done with Umi Hotaru, you can choose to either go all the way to Chiba, and have a drive around the bay to get back to Tokyo, or you can U-turn at Umi Hotaru and come back the way you came. The Weekends do tend to be really crowded, and cars can wait upwards to three or four hours to get a parking spot at Umi Hotaru on national holidays.

GOOGLE MAP DIRECTIONS (from Shinagawa Station): https://www.google.co.jp/maps/dir/%E6%9D%B1%E4%BA%AC%E9%83%BD%E5%93%81%E5%B7%9D%E9%A7%85/STARBUCKS+COFFEE,+Nakajimachisakiumihotaru,+Kisarazu,+Chiba+Prefecture+292-0071/@35.5323277,139.7538333,12z/data=!3m2!4b1!5s0x601871c824ed2ac1:0xcae94016d8b917d7!4m13!4m12!1m5!1m1!1s0x60188a5070e119cb:0x252c5ac6efd2689c!2m2!1d139.74044!2d35.630152!1m5!1m1!1s0x601871c82474b845:0x5822d102b8f5511!2m2!1d139.874078!2d35.464341