The Esterteng is the region of eastern Acirca to the south of the Estring Mountains, which mirrors the similar curved landmass of western Acirca (which is the setting of Rice Boy). It is surrounded by the Circle Sea to the west, and the Esteret-- separating Acirca from Grenth-- to the east.
The Esterteng is vertically bisected by a large waterway which is analogous to the Sunk River. It travels south from the Estring Mountains to the central Esterteng, where it forks into two distributaries, the River Tarria (which continues south) and the River Asria (which heads west to Circle Sea). Located at this split is the city of Sahta, one of the major locations in the region. It was (presumably) the capital of the Sahta Empire, which existed in the early and middle Blue Age.
The south-central Esterteng, known as the Flutelands, is the setting of Vattu. This was determined before the comic began by hints gleaned from pre-release graphics like the Vattu-themed site header.<ref>http://www.rice-boy.com/site/diskvattu.png</ref> The Flutelands are divided from the northern Esterteng by an unnamed mountain range.