Pantheon has an odd portico that suggests a change during construction.
That's been a puzzle for a long time. I read a cogent explanation not that many years ago, but it's not in the noggin, or at least it's not near the top of the pile. The other possiblity was that just the portico was original, and the rest of the temple built by Marcus Agrippa was wood and brick, didn't survive the fire of Rome, and the portico was left standing./blockquote>