Not far from Kobe. You can walk over Rokko Mountain, if you want to go that way. This is a hot spring town but, if you are not into baths it is still a good walking place especially in winter when you will probably have snow. There are a number of ways to get to Arima. Bus from Kobe, or take the Kobe subway to Tanigami and change there for the Kobe Dentetsu Line for Arima-onsen. You may have to change at Arimaguchi. Or you can take the rope way across Rokko and down the other side.
photo by 663highland