Japan: Fuji-Q. Japanese version of Six Flags but with more world Guinness records.

Right by Mt. Fuji, there is an amusement park just like Six Flags here in the USA (just a little more intense).

Why?

All the Guinness World Records!

1. FUJIYAMA (Roller coaster) 79m tall, Max speed 130km/h
2. Giant Coaster (Roller coaster, no longer existing) 1,380m long
3. Skate Rink (26,500 meters squared)
4. Moon Scramble (66m tall, Max speed 105km/h, 6.5G)
5. Longest maze/haunted house 500m-700m
6. Dodonpa (Roller coaster) Max speed 172km/h
7. EEjanaika (Roller coaster) Most spins 14 times
8. And finally, the picture below shows one of their roller coasters with the world record of the most steepest fall: 121 degrees.

There is a bus operating from major stations (e.g. Shinjuku station, Yokohama station). Usually you can buy a package which includes the bus ride + ticket. Usually costs around $100. 

You'll get to enjoy the view of the beautiful Mt. Fuji, recently named a world heritage. 

Great food courts (mostly fast food, but we all know fast food shops in Japan are amazing) and clean fresh air. 

Make sure you stop by the service areas (on the highway) if you are driving there. Japanese service areas on the highway are superb. Great restaurants, fun street food and is the best place to buy gifts for your coworkers. More on that later :)