Sea Lion Caves is a connected system of sea caves and caverns open to the Pacific Ocean in the U.S. state of Oregon. They are located north of Florence on U.S. Highway 101, about midpoint on the Oregon Coast. In this area Highway 101 follows a steep and undeveloped seascape above sea level. Human access to the caves is through a gift shop building. Description The cave system is at sea level and the ocean continually washes into the main cavern which has a floor area of about and a vaulted rock dome about high. Southward from the main chamber, a low passage runs to a sea level opening. This corridor is flooded at high tide and free of water at low tide. The western entrance is a short, high passage through which the ocean washes at all tide levels. At the north, a third entrance is about above the ocean which serves as an elevated observation area where the entire cave system and its wildlife are visible. Lichens, algae, and mineral stains cover the cavern walls with greens, pinks, purples, buffs, and reds on the rough surfaces, some of which are named Lincoln's Head, the Indian Maiden, and The Goddess of Liberty. The sea level portion of this cave and the sea cliff rocks just outside the cave have become, over the centuries, the only known mainland rookery and hauling area (wintering home) of the Steller's sea lion and—to a lesser extent—the California sea lion. The high vault is a natural resting place for sea birds. Many birds make their home at or near the Sea Lion Caves such as the pigeon guillemot, Brandt's cormorant, western, herring, and California gulls, tufted puffins, and the occasional hawk or bald eagle. Sea Lion Caves is one of the great sea caves of the world, and currently ranks 10th among the world's longest sea caves. With a measured length of 1315 feet, it is the longest in the United States. A comparable cave is the undeveloped Painted Cave on Santa Cruz Island, California, which is 1227 feet long. The whale watching deck, located below the gift shop, permits a seaward view of approximately . The deck is at an elevation of , making it a popular whale watching post. Typically, orcas are seen migrating once a year past the Sea Lion Caves, whereas the gray whale is seen anywhere from a few