One of your first stops should be Tarui Tourist Information Center. Here, you'll be able to orient yourself and get some great ideas before you start exploring.
This tourist information center is in Tarui, a place that has lots going for it! Sekigahawra Battlefield, Site of Reversible Destiny, and Yoro Park are other worthwhile sightseeing options close by when you've had your fill of Tarui Tourist Information Center.