Temple of the Sun, Machu Picchu, c. 1450 — the curved wall of this semi-circular tower represents the finest ashlar masonry at the site, with trapezoidal windows aligned to admit solstice sunlight onto a sacred stone inside. Beneath the tower, a natural cave was shaped into a royal mausoleum with carved niches for ritual offerings.
© bobistraveling, CC BY 2.0, via Wikimedia Commons