Mimas - A moon of Saturn which from certain angles looks like a death star. [1]
Hyperion - Another moon of Saturn which looks like a sponge. [2]
Phobos - A moon of Mars with a huge crater on one end.[3]
[1] - https://en.wikipedia.org/wiki/Mimas_%28moon%29 [2] - https://en.wikipedia.org/wiki/Hyperion_(moon) [3] - https://en.wikipedia.org/wiki/Phobos_(moon)
Phobos monolith
https://en.m.wikipedia.org/wiki/Phobos_monolith
Good ol Buzz, giving mention to the subject
https://m.youtube.com/watch?v=bDIXvpjnRws
Also, Mars monolith https://en.m.wikipedia.org/wiki/Mars_monolith
Europa is another intriguing spaceball, with the (vague if you must) possibility of a life-supporting ocean.
Edit: add mars monolith
https://en.m.wikipedia.org/wiki/Janus_(moon)
https://en.m.wikipedia.org/wiki/Co-orbital_moon
Mimas - A moon of Saturn which from certain angles looks like a death star. [1]
Hyperion - Another moon of Saturn which looks like a sponge. [2]
Phobos - A moon of Mars with a huge crater on one end.[3]
[1] - https://en.wikipedia.org/wiki/Mimas_%28moon%29 [2] - https://en.wikipedia.org/wiki/Hyperion_(moon) [3] - https://en.wikipedia.org/wiki/Phobos_(moon)