To be fair, Neptune and Uranus are technically classified as "Ice Giants" so yeah, you could walk on them, maybe. Also, why the hell not. Maybe Neptune/Uranus (one of the two because there practically the same) could be like that one star wars movie where Obi wan had to go to inspect the planet they were making the clones. They could have like these platforms with ruined buildings sinking into the gigantic ocean, Also the whole damn setting of Destiny is based off the "Travelers Grace" and how we can go onto Venus without dying instantly from the methane air, so don't go saying that "oh that's not possible" or "it's just not realistic", it's a video game.