Nebuchadnezzar dreamed of a statue. Daniel interpreted it as four successive empires: Babylonia, Medo-Persia, Greece, and Rome. Each was replaced by the next until a rock not cut by human hands destroyed them all. Daniel 2 is one of the most remarkably specific prophetic passages in Scripture.
The fish symbol used by early Christians is called the Ichthys.
In Greek it spells ΙΧΘΥΣ (Ichthys), meaning “fish,” but the letters also form an acronym:
Iēsous - Jesus
Christos - Christ
Theou Huios - Son of God
Sōtēr - Savior.
In the early church, believers often used this symbol as a way to identify fellow Christians.