Situated south of the Unzen Onsen Town and just beyond the Kojigoku Onsen, the Houbaru area is known for about 50,000 trees of the colony of Miyama-kirishima (Kyushu azalea) spreading at the foot of Mt. Takaiwasan. This area has been developed as the "Houbaru Garden". If you take a walk along the Kyushu Nature Trail, that runs through the area, you can see Miyama-kirishima and other kinds of azalea such as kobano-mitsuba-tsutsuji and yama-tsutsuji, listen to the birds singing here and there, and feel close to the nature.