Assuming you want this in minifigure scale, I would mount part 553c Brick, Round 2 x 2 Dome Top - Hollow Stud with Bottom Axle Holder x Shape + Orientation upside down in the wall, topped with a 18674 Tile, Round 2 x 2 with Open Stud in Black mounted right-side up. You will need to do some clever SNOTting to make that all fit, but an upside-down 3659 Brick, Arch 1 x 4 could hold the dome brick and the round tile can be held in place with a regular brick.


Here is how this would look like:



Note: technically this doesn’t fit (the dome sticks out of the top of the inverted arch brick by just a smidge too much) but due to tolerances you can make this work. I used a white dome brick because I didn’t have a trans-clear one handy.