Original: He undertook gigantic projects, including the first version of the Great Wall of China, the now famous city-sized mausoleum guarded by a life-sized Terracotta Army, and a massive national road system, all at the expense of many lives.
Simplified: They had a lot of huge projects, including the Great Wall of China, a city-sized mausoleum guarded by a life-sized Terracotta army, and a system of roads that went all over the nation.