The Grand Pantheon was a temple built in the very early days of ancient Rome. It was dedicated to all the Roman gods. First, it was made of wood but it burned down. Next, the Romans used concrete (one of their inventions) to make this large building and dome. Still today, it is one of the largest single-span domes in the world. The dome is in the back and eight large columns are in the front.
The word Pantheon means "temple of all the gods." Today it is used as a church. People like to visit it and tour it because it is the building in the best shape that was built by the ancient Romans. Admission is free and it is open all but three days out of the year. It is closed Christmas Day, New Years Day, and May 1st.
This building influenced how many other places built their buildings. Many state capitol building in the United States have domes and columns.