I think that Beppu is definitely one of the "must see" places in japan. Not
only that you can enjoy many onsens, but you also can try "wild"
hotsprings in the mountains, jigokus, visit monkey park where you can see
more than thousand wild monkeys. To see all of this you will need about 2
days.
Visit official Beppu city guide web pages for more information about the
city here:
BEPPU CITY GUIDE
Regards,
Bibo
HAPPY NEKO Backpackers - Happy Neko Backpacker, Beppu