The Holy of Holies
Each curtain was 20 cubits wide, 40 cubits tall, and 1 handbreadth thick. They were woven of wool dyed with many colors at an incredible cost of 820,000 golden dinars (according to one opinion). It was described as “the most praiseworthy item in the world.” Spanning the top was a band of gold, 2 handbreadths tall and 2 fingerbreadths thick, which kept it taut so that the entire width of the Holy was covered (the curtain of the Antechamber also had such a feature).
The outer curtain was folded back at the southern end and held by a golden band and the inner curtain was similarly folded back at the northern end. This allowed the Kohen Gadol to walk between them without having to open them manually as he entered the Holy of Holies on Yom Kippur while at the same time they completely blocked off the interior of the Holy of Holies from the view of anyone standing in the Holy.
The innermost chamber of the Sanctuary was the Holy of Holies. It measured 20 cubits (30 feet) square and, like the Holy, was plated with gold and set with precious stones. Protruding 3 fingerbreadths (2¼ inches) above the floor was the Foundation Stone and on this stone they placed the Ark during the First Temple era. In the Second Temple the Holy of Holies was empty since the Ark had been concealed in a labyrinth of underground tunnels before the First Temple was destroyed. The Holy of Holies also had windows which, according to Josephus, were angled so that no one could see in from the outside.