Why go
The most impressive engineering is often easy to walk past. Terraces are layered to absorb and move water; channels and drains protect built spaces; stone blocks fit closely without mortar. These choices explain how a settlement could occupy such a narrow, wet mountain ridge.
The full story
Building at Machu Picchu meant working with limited flat ground and substantial rainfall. The Inca made terraces with layers of stone and soil, giving slopes usable surfaces while helping water drain through them. Channels carried water across the settlement, and hidden drainage reduced the pressure of rain beneath plazas and buildings. Stone for many walls came from the mountain itself. In important structures, builders cut blocks to fit tightly without mortar. Trapezoidal openings and walls that incline slightly inward are among the forms associated with Inca construction in seismic country. These are not separate tricks: together they let buildings sit on a steep ridge where water and ground movement mattered. The exact methods used to shift the largest stones are still debated. Focus instead on what remains visible: the join between blocks, small drainage openings and the way each terrace supports the level above it.