Tokyo Dome is the centrepiece of Tokyo Dome City which also includes a shopping complex, upmarket spa, and a theme park. The stadium itself is some to Tokyo’s Yomiuri Giants baseball team but is used to host a wide variety of events, exhibitions, and shows.
While there isn’t a huge amount to do in the surrounding area without crossing the river south into Kanda and Jimbocho, Koishikawa Rakuen Garden is definitely worth a stop.