#Cornerstone September 19

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September 2026 several of us are going to take on the 30-Day Architectural Coach4aday Challenge each day, we will define an architectural term and provide examples of where it is located. This challenge will let observation, travel, history, and photography all intersect. For Day 19 it is the CORNERSTONE.

Like many things in architecture, the purpose of a cornerstone has changed from the 19th to the 21st century. Two hundred years ago, it served as a physical reference point, establishing the level, angles, and alignment of the entire masonry foundation. It was an important structural element that helped support the weight of the building. Today, the cornerstone is primarily ceremonial and symbolic, as modern construction methods and materials have made its original structural purpose largely obsolete.

30-Day Architectural Challenge Guidelines

If you have ever watched Seinfeld, you know that George Constanza always wanted to pretend to be an architect.

Well, this month’s challenge let’s all of us that are not architects learn a little more about their language. To do that we have a simple challenge.

Every day we’ll learn one architectural term. Your challenge is to find an example—preferably one you’ve actually seen—and share a photograph, location and brief explanation.

Day-19 Cornerstone