▶Oyama Observatory
https://www.vill.aogashima.tokyo.jp/star/sea/place.html
Aogashima, described as an "isolated island in the middle of the ocean," boasts spectacular views.
From the outer rim, which has a large convex part that has been selected as one of the 10 New Tokyo Views, you can see Maruyama, the inner rim of the double caldera. From late October to early April, you can see Canopus, a star that appears just above the horizon in the southern sky, which is rare in the northern hemisphere.