Bartholomew (Nathanael) was prejudiced against Jesus because Jesus came from Nazareth (Jn 1:46). But after Jesus mentioned He saw Nathanael under the fig tree, Nathanael changed completely, from prejudice to faith, and acknowledged Jesus as "the Son of God" and "the King of Israel" (Jn 1:49). Why was Nathanael so impressed by Jesus' remark that He saw him under the fig tree? What was Nathanael doing under the fig tree?
No one knows why the fig tree was so significant to Nathanael. Some Bible commentators mention that the fig tree is symbolic of the Israelite nation (see Mk 11:12ff). Thus Jesus' reference to the fig tree would have special symbolic significance.
Others see Jesus using the supernatural gift of knowledge, as He did with the Samaritan woman at the well (Jn 4:18). Jesus could have been noting a secret sin Nathanael committed under the fig tree (see 1 Cor 14:24-25).
Another possible interpretation is that Nathanael was praying under the fig tree, praying for the coming of the Messiah. Jesus presented Himself as the immediate Answer to Nathanael's prayer.
On this special feast day, let the Lord speak to you symbolically, prophetically and prayerfully. You'll never be the same.