The Pantheon

By Jakob Alt - repro from artbook, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10206191

The Pantheon is a massive temple first commissioned by Agrippa, Augustus's right-hand man. The current building was completed by Hadrian, after the previous had burnt down. The building is composed a dome (the Cella) with a columned facade (called the Portico still containing the original inscription) practically bolted onto the front. Interestingly, the coffered dome is not actually closed, sunlight streaming in through the aperture where the dome's apex should be, allowing sunlight (and rain) to stream onto the floor. The columns within are all carved from single pieces of marble, some of yellow marble, some of white, and some with marble with purple veins. Raphael's tomb was placed within at that artists behest. Niches all along the back of the interior held statues, either to the Olympian gods or to chief figures of state such as  Hadrian himself, or both of these at different times.

When a site has such an enormous reputation and pedigree as does the Pantheon, anyone with the chance ought to take out the time to see it. Rarely do places such as these occupy such an abnormally large part of popular culture and tourism without having something worthwhile to be gained from visiting them. If you're not impressed, at least you'll be able to say you know what everyone is talking about, finally.