Deuteronomy 3:4 (ESV)

4 And we took all his cities at that time there was not a city that we did not take from them sixty cities, the whole region of Argob, the kingdom of Og in Bashan.

Israel's victory was a massive success, with sixty cities taken. The northern Transjordan region (Bashan) had been home to many settlements, largely on account of the fertility of the soil. Argob was the eastern area of Bashan.