I have attended games at the Seibu Dome in 2008 and 2012. Although it is not the best baseball stadium in Japan from a design / facility / amenity point of view, it is actually my favorite place to watch a baseball game in Japan. The reason for this is very simple - good sightlines, relaxing environment and pleasant surroundings. Fans are not so rabid - at least in the two games I attended - that they became a distraction in their intensity.
The stadium design is one of a kind. The stadium is called a dome, but it was originally built as an outdoor stadium - all in a single level seating bowl so typical of many Japanese ballparks. A number of years later, a dome was added over the top of the seating bowl and field, but it was built up on supports, not attached to the seating bowl. As such there is about a 10-20 foot gap between the stadium itself and the dome and from most seats in the stadium, one can see outside.
The stadium is entered from the outfield and you must go into the gate that corresponds to whether your seat is on the first base or third base side. Concessions are located on the outside of the concourse - effectively outdoors, as are restrooms. The team used the posting money received from the Red Sox for signing Daisuke Matsuzaka to spruce up the facillty, adding two sections of in grandstand concession stands and considerably upgrading the scoreboard technology. Neither improvement changed the character of the place however.
A branch line of the Seibu private railway will bring you right to the forecourt of the Seibu Dome, with a long walkway lined with concession stands and with fight song / pep music playing in the background. The downside is that unless you catch one of the three or so direct trains between the Seibu Railways station at Ikebukuro (adjacent to the JR station and subway station) to the ballpark both before and after the game, you will have to change trains at Nishi Tokorozawa to travel between Ikebukuro and the ballpark. Changing trains on the way to the stadium involves staying on the same platform. One must change platforms on the return journey. Thus, the ballpark is not the easiest of the Japanese ballparks to travel to, but in my view the trip is well worth it.
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