Take a look around this panoramic view. Pay particular attention to the semi-circular cobblestone design in the street. Try to recreate a drag-testable construction of this street using the GeoGebra applet below.
X(5) in Kimberling's Encyclopedia of Triangle Centers, is the center of the nine-point circle, which is the unique circle passing through the midpoints of the sides of the triangle. The radius of the nine-point circle is one-half the circumradius.