Blue Hole (Red Sea)
The Blue Hole is a diving location on the southeast Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.
Blue Mountain (Pennsylvania)
Blue Mountain Ridge, Blue Mountain, or the Blue Mountains of Pennsylvania is part of the geophysical makeup of the Ridge-and-Valley Appalachians in the U.S. state of Pennsylvania. It is a ridge that forms the southern and eastern edge of the Appalachian mountain range spanning over from the Delaware Water Gap as it cuts across the eastern half of the state on a slight diagonal from New Jersey tending southerly until it turns southerly curving into Maryland, and beyond.