Replacing much simpler predecessors, the first more formal, stone built agricultural terraces were constructed in Peru in the middle of the first millennium AD. The most obvious use of these platforms in the hillside is that they counteract soil erosion. But there is more to it than that. By Inca times the technology of the terrace, efficiently watered by irrigation canals, had been perfected. The sophistication of these systems and the effort that went into their construction is truly remarkable.