Obscure places are fun to visit, especially when they involve a light blue sky dome in a surgical amphitheater built in the 1800s. We recently followed this link from Atlas Obscura and found the Ether Dome at Massachusetts General Hospital, where the first use of ether anaesthetic was used in 1846.
The Ether Dome is located at the 4th floor of the Bulfinch Building, feel free to ask the information desk staff and they'll gladly point you to the right direction. Note that there'll be times where the dome will be closed, since it's still in use for occasional medical seminars/events.
We loved how historical this place is, so gracefully preserved, yet feels very modern and minimal at the same time. We highlight recommend paying this unconventional space a visit next time you're in Boston.