Why is the arc de trompie there?

How many square acres of water are there in the Hoover Dam? How far is Austin Texas from the Grand Canyon? How does distance from the sea affecting temperature? Explain in details the manufacturing process of cement with neat sketch? Which river flows through st davids? When did the Mississippi River freeze over in 1942? When did Magic Johnson Get a star on the Hollywood walk of fame? What Ocean state is closest to Massachusetts? How do you make a coin disapear? Why did the Panama Canal need locks? What are two questions Erie canal developers might have asked English before building the canal? Where is the kaghan valley situated? What country has the largest area of temperate deciduous forest? Is the US Coast Guard going to burn the oil spill in the Gulf of Mexico? The entrance to which museum lies below a glass pyramid? What is the meaning of small world? What is tourist and excursionist? Which is the country has seven seas? What rock is the monument to four American presidents in mount Rushmore in America made from? What do the people in the rainforest know a lot about that can help us when we are sick?