An unexplored place is one where people have not been to find out what is there.

unexplored territory 未经勘察的地域

An unexplored plan, idea, or subject is one that has not been examined to find out what it involves.

The subject of alternative medical care for older people has been entirely unexplored. 尚未有人就替代性老年人医疗保健这一问题做彻底研究。