Do you know the differences between the new building and the old ones

Do you know the differences between the new building and the old ones
Old buildings 66 brick(砖)and stone walls.The walls hold up the 67 .
In cities,many modern building 68 as if they are made just of windows.Walls of dark glass reach high into the air.Many buildings are 69 than 50 stories(层)tall.
Are walls of glass strong 70 to hold up the new buildings No,The new glass walls do not hold up the buildings,71 they only cover up the frame(框架)made of steel.Have you ever watched a new building going up The steel frame is built 72 .Then the glass walls are hung on the frame.When the building is 73 ,the frame does not show.The outside looks like windows without walls.The glass walls shine 74 the sun with no decoration(装饰).Many people find 75 beautiful just as they are.