For the first time in more than 70 years, the space beneath MIT’s iconic dome has been restored to its original splendor. The dome of the Barker Library reading-room rotunda, whose diameter and height are both 75 feet, is nested inside the 100-foot-wide Great Dome; the two domes converge at the circular oculus, an intricate 27-foot skylight set in the center of both. The skylight was sealed over in 1942 to keep the dome from being a bombing target. After being briefly uncovered in the 1950s, it was then sealed again, probably because of leaking. Now, with sunlight streaming through the restored oculus and the rotunda freshly repainted, the nickname “Barker batcave” no longer applies.