Bodie Island Lighthouse, Nags Head, North Carolina

© Michael Ver Sprill/Getty Image

Sentinels of the sea. National Lighthouse Day

Happy National Lighthouse Day! A beacon, a warning, and a symbol of hope and home, lighthouses have existed for thousands of years. The earliest known was the Pharos of Alexandria, which stood an estimated 330 feet tall. Built by the ancient Egyptians in the 3rd century BCE, an open fire was lit at its highest part to guide ships into port. Illumination technology advanced over the centuries, culminating in today's electric versions beaming light that can be seen from over 20 miles away. North Carolina's Bodie Island Lighthouse, pictured here, was built in 1872 and overlooks a section of ocean once known as the Graveyard of the Atlantic. Since then, it's been doing its best to outshine the stars above, as it guides sailors home to safe harbor.