The Garamantes also engaged in the trans-Saharan slave trade. The Garamantes used slaves in their own communities to construct and maintain underground irrigation systems known as the "foggara". Early records of trans-Saharan slave trade come from ancient Greek historian Herodotus in the 5th century BC, who records the Garementes enslaving cave-dwelling Ethiopians. Two records of Romans accompanying the Garamentes on slave raiding expeditions are recorded - the first in 86 CE and the second a few years later to Lake Chad. Initial sources of slaves were the Toubou people, but by the 1st century CE, the Garmentes were obtaining slaves from modern day Niger and Chad.