outdoors 12,439, background 11,172, outside 10,295, tree 8,208, sky 8,005, city 6,632, clouds 4,374, trees 4,036, vehicle 3,835, window 3,381, cloud 2,568, train 1,930, electric 1,424, building 1,315, windows 1,096, buildings 821, urban 631, travel 485, bridge 446, wire 253, traveling 230, railroad 188, trains 119, transportation 97, electric power 94, electric wire 46, electric train 46, electric locomotive 41, passenger train 40, elevated 7, power line 7, railcar 5, passenger locomotive 3, railroad bridge 3, elevated train 2

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