J-PARC is being constructed at the Tokai site of Japan Atomic Energy Agency [JAEA] in the Tokai Village, which is located at 100km northeast of Tokyo and 70km north of the Tokyo-Narita International Airport. Mito City (or simply called "Mito" in Japan) is adjacent to Tokai. Mito is the largest city in Ibaraki Prefecture (and the seat of the government) and has many historic spots.
Ibaraki "Trotter" Guide
(with the guide to Mito)
[pdf]
High Energy Accelerator Research Organization
[KEK]
is in
Tsukuba City,
which is in the west of
Tsuchiura City,
and Tokai is located at 50km northeast of KEK.
It takes 80 minutes to drive from KEK to Tokai.
Both Mito, Tokai, Tsukuba and Tsuchiura belong to Ibaraki Prefecture; Tokyo-Narita International Airport belongs to Chiba Prefecture in the south of Ibaraki.