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.
Height: 146m (481ft) The oldest of three pyramids on the outskirts of Cairo, The Great Pyramid of Giza was built as a tomb over a 10 to 20-year period ending around 2560BC. It was originally 146.5 metres tall but erosion has reduced its height to 138.8 metres. It is the only surviving Wonder of the Ancient World.