In 1889, this observatory was completed to hold what was at one time the world’s largest telescope. This original 18.5-inch diameter telescope is still in use as an important teaching tool in Northwestern's astronomy program. Designed by Cobb and Frost, the Richardsonian Romanesque building was the gift of James B. Hobbs, a Northwestern trustee from 1883 to 1914, and features rough-cut limestone walls, a broad entrance arch, a slate roof, and eyebrow dormers. In order to minimize vibrations, the core pillar on which the telescope stands is structurally isolated from the rest of the heavy stone structure. The entire building was laboriously moved several hundred feet over a three-month period in 1939 to make way for the construction of the Technological Institute. In 1997, the old hand crank-operated dome was replaced with the current shiny aluminum cover with electric motor operation.