This is the inside of the southern-most submarine observation tower at Cape Henlopen State Park. I understand there are 7 towers in the park, one has been restored and can be toured, just not at 5AM. The bottom of the door was rotted on this one, so I climbed in. I have a bunch from the outside at sunrise, I’ll be posting one of them soon.
Note the bands of orange light between the openings; it is from the rising sun shining through the openings over my head.