AI – ‘No. The width at the top and base of these archways is not the same. They are defined by a wider base and a narrower top, a structural choice known as a trapezoidal shape. 

While this form is most famously associated with Inca architecture in South America, it also appears in various contexts in Egypt and Mesopotamia—though its use and frequency differed across these regions.

Region-by-Region Breakdown

South America (Inca Empire)

The Inca are the most prolific users of the trapezoidal archway. 

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• Design: Every doorway, window, and wall niche at sites like Machu Picchu is built with inward-sloping sides.
• Purpose: The wider base provides exceptional seismic stability, allowing structures to withstand the frequent earthquakes of the Andes.
• Consistency: The angle of the sides is remarkably consistent, often measured at approximately 4.5 to 5 degrees. 

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Ancient Egypt

In Egypt, the trapezoidal shape was primarily used for monumental gateways (pylons) and specific functional openings. 

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• Design: Temple pylons are much wider at the base than the top, creating a stable, sloping facade.
• Ventilation: Roof openings were often trapezoidal or conical to create a pressure difference that accelerated airflow, cooling the interior.
• Comparison: Unlike the Inca, many Egyptian residential doors and windows remained strictly rectangular, though grander ceremonial entrances adopted the tapered look. 

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Mesopotamia

Mesopotamian architecture utilized the trapezoid mainly in the construction of Ziggurats and massive mud-brick walls. 

• Design: Walls were frequently built with a batter (a slope where the base is thicker/wider than the top) to support the immense weight of mud-brick tiers.
• Mathematics: Babylonian mathematicians were highly advanced in calculating the areas of trapezoids, often using them as models for land measurement and architectural planning.
• Entrance Style: While arches were later developed (like the Ishtar Gate), early doorways were often simple rectangles or tapered openings in heavy, inclined walls. 

Key Structural Benefit: In all three regions, the wider base and narrower top served to distribute weight more efficiently toward the ground, reducing the stress on the lintel (the top horizontal beam) and improving overall structural longevity.’