The world-famous Louvre Museum in Paris is almost 500 years old, and it faced a very modern problem: There simply wasn’t enough space for six million visitors each year. In 1989, American architect I.M. Pei designed a striking glass pyramid in the building’s center to be a visitor‘s entrance and shopping arcade. But he also started an angry debate. Some people felt his glass building was a piece of art, like the ones inside the museum. Others said it was just an ugly, modern mistake.