Tuesday marks the twentieth anniversary of first game ever at the Tokyo Dome, the first domed stadium in Japan. Built on the site of Korakuen Stadium, it has been home to the Giants since it opened and was the home of the Fighters until they moved to Sapporo after the 2003 season. It's been the site of a couple major league baseball games (Mets & Cubs in 2000, Yankees & Devil Rays in 2004 and the upcoming Red Sox & A's series), the Asia Cup series every year since 2005, and one of the first rounds of the World Baseball Classic in 2006. Wikipedia has an article on the dome here.
There are now five other domes in Japan, meaning that half of the twelve teams play indoors (although a couple domes have retractable roofs).
Calbee had a 6 card subset in their 1988 set commemorating the new stadium, nicknamed (at the time) "The Big Egg". Here's two of the cards:
(As usual, thanks to Japan Baseball Daily's "Today In Japanese Baseball History" for the tip.)