Pantheon
This is the most impressive ancient building in Rome. Like the Colosseum, it was built of concrete, and has been in pretty much continuous use since it was put up by Hadrian (not Marcus Agrippa as the inscription indicates; he was responsible for an earlier building that burned in 80 AD). It started out as a temple and has been a Christian church since the seventh century, which saved it from being used as a quarry or worse as the Colosseum was. After the fall of Rome, the secret for making concrete was lost to the western world for a thousand years.
It is very difficult to photograph the interior satisfactorily, but I think I got lucky with this shot.
Pantheon
This is the most impressive ancient building in Rome. Like the Colosseum, it was built of concrete, and has been in pretty much continuous use since it was put up by Hadrian (not Marcus Agrippa as the inscription indicates; he was responsible for an earlier building that burned in 80 AD). It started out as a temple and has been a Christian church since the seventh century, which saved it from being used as a quarry or worse as the Colosseum was. After the fall of Rome, the secret for making concrete was lost to the western world for a thousand years.
It is very difficult to photograph the interior satisfactorily, but I think I got lucky with this shot.