Do you know the differences between the new buildings and the old ones?

    Old buildings h  brick and stone walls. The walls hold up the buildings. In cities, many modern buildings l  as if they are made just of windows.

    Walls of dark glass reach high into the air. Many buildings are m  than 50 stories tall.

    Are walls of glass strong e  to hold up the new building? No. The new glass walls do not hold up the buildings, but they only cover up the frame made of steel. Have you ever watched a new building going up? The steel frame is built f  . Then the glass walls are hung on the frame. When the building is f  , the frame does not show. The outside looks like windows without walls. The glass walls s  in the sun with no decoration. Many people find them beautiful just as they are.