Caving—also occasionally known as spelunking in the United States and Canada and potholing in the United Kingdom and Ireland—is the recreational pastime of exploring wild (generally non-commercial) cave systems. In contrast, speleology is the scientific study of caves and the cave environment. Caving is often undertaken for the enjoyment of the outdoor activity or for physical exercise, as well as original exploration, similar to mountaineering or diving. Physical or biological science is also an important goal for some cavers, while others are engaged in cave photography. Virgin cave systems comprise some of the last unexplored regions on Earth and much effort is put into trying to locate, enter and survey them. In well-explored regions (such as most developed nations), the most accessible caves have already been explored, and gaining access to new caves often requires cave digging or cave diving.