Darius crossing the Bosporus by unknown artist 1904

"The kings of the aforesaid nations having gathered, then, the Scythian messengers came and laid everything before them, explaining how the Persian, now that the whole of the other continent was subject to him, had crossed over to their continent by a bridge thrown across the neck of the Bosporus, and how having crossed it and subjugated the Thracians he was now bridging the Ister, so as to make that whole region subject to him like the others."

-Herodotus, The Histories, Book 4.118

Source:

https://archive.org/details/dariusgreat00abboiala/page/n5/mode/2up

https://commons.wikimedia.org/wiki/File:Darius_crossing_the_Bosphorus.jpg

Quote:

https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Herodotus/4F*.html