Here's an example of a very subtle truth that is revealed in the Bible that I like.
Isaiah was a prophet who lived in Jerusalem about 600 years before Christ was born. At about this time, the ancient Greeks were only just starting to sail around the Meditteranean and map out their islands. It wasn't until 200 BC that a Greek mathematician calculated what he thought was the circumference of the earth.
But in a description of God's majesty, it is recorded in Isaiah 40:22a:
He sits enthroned above the circle of the earth,
and its people are like grasshoppers.
If not for divine inspiration, I seriously doubt he would have known the earth was round. To think that there was a time when some people even thought the earth was actually flat.