The Incircle of the Medial Triangle. The center of the Spieker circle is called the Spieker Center.
See also Incircle, Medial Triangle, Spieker Center
References
Johnson, R. A. Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle. Boston, MA:
Houghton Mifflin, pp. 226-228, 1929.