Vertical lines are straight lines that run up and down, perpendicular to the horizontal lines. They are often used in art, design, and architecture to create a sense of height and stability. In mathematics, vertical lines can be represented on a graph, where they indicate a constant value of the x-coordinate. In everyday life, vertical lines can be seen in structures like buildings and trees. They help to define shapes and create visual interest. For example, the Eiffel Tower features many vertical lines that contribute to its iconic silhouette, emphasizing its towering presence against the sky.