Daniel 8:2 (ESV)

2 And I saw in the vision; and when I saw, I was in Susa the citadel, which is in the province of Elam. And I saw in the vision, and I was at the Ulai canal.

First, something special happens. The Lord takes Daniel to another place. He is now no longer in Babylon but is suddenly moved to the citadel of Susa in the province of Elam. This is more than 400 kilometers east of Babylon. Why does the Lord bring him here to see this vision? One reason is that the Lord is showing Daniel that the Medes and Persians will take over power in Babylon. His vision is of the year when the united powers of these two nations begin to threaten the Babylonian Empire and conquer the Province of Lydia, capturing it from Babylon. Susa becomes the capital of the Median-Persian Empire and it is here that we also meet king Ahasuerus and his queen, Esther at a later date.