Building techniques improved, iron became more common, and hydraulics were used to dig riverbeds deeper. So less floods happened that destroyed farms and endangered lives.
The natural resources included gold, diamonds, cooper, cobalt, and rubber. These resources were tapped by the native Congo population through a system of slave labor implemented by King Leopold II. This made the Belgian government/economy prosper at the hands of the slave laborers in this country. This brutal regime resulted in the deaths of thousands of Congo citizens.
Yes, Spain did control the Incas and Aztecs for gold so he could promise the Spanish for the gold. (He promised them thats why he took over)
