Exploring the deep ocean floor: Hot springs and strange creatures. The ocean floor is home to many unique communities of plants and animals. Most of these marine ecosystems are near the water surface, such as the Great Barrier Reef, a 2,000-km-long coral formation off the northeastern coast of Australia.
Quick Answer. Egyptian pyramids often took 10 years or more to complete. According to the Greek historian Herodotus, the Great Pyramid at Giza was built in 20 years by 100,000 workers and was meant to be a tomb for Pharaoh Khufu.
But the process of building pyramids, while complicated, was not as colossal an undertaking as many of us believe, Redford says. Estimates suggest that between 20,000 and 30,000 laborers were needed to build the Great Pyramid at Giza in less than 23 years. By comparison, Notre Dame Cathedral in Paris took almost two hundred years to complete.