The Inca Empire is known for its extensive road system and military conquests, which spanned across much of western South America. The Incas developed a sophisticated network of over 25,000 miles of roads, known as the Qhapaq Ñan, which facilitated communication, trade, and the movement of armies throughout their vast territory. This infrastructure was crucial for maintaining control over their empire, which reached its height in the 15th century. The Incas' military prowess and organizational skills allowed them to conquer and integrate various cultures, leaving a lasting legacy evidenced by archaeological sites like Machu Picchu.