“Now behold, your servant has found favor in your sight, and you have magnified your lovingkindness, which you have shown me by saving my life; but I cannot escape to the mountains, for the disaster will overtake me and I will die; now behold, this town is near enough to flee to, and it is small. Please, let me escape there (is it not small?) that my life may be saved.” Gen. 19:19-20
Previously called Bela (Gen. 14:2), Zoar was the smallest of the five towns of the plain. Lot may have thought he could not have made it any further by the time destruction would come. The angels spare Zoar from destruction on account of Lot (v. 21) though Lot ultimately heads to the mountains.
Robert Alter notes that Lot was not up for attempting to live in the wilderness having become accustomed to the city life, and only ultimately heads to the mountains for fear of destruction.