Where to claim?

Space is enormous, so you might ask, What should I claim? Well, there are a lot of places in space, and many of these are probably worth claiming, but a good place to start would be one of our own planets. These are certainly worth claiming; the inner, rocky planets and the many dwarf planets have vast mineral resources and incredible landscapes, the gas giants have dozens of moons with these and are also valuable sources of hydrogen and helium, and the ice giants have all of these plus their impressive appearance. But you can't claim all of the solar system; other nations are certain to go to war with you over that! A better idea might be to claim a portion of the Moon, or of Mars or Venus, or a single moon of one of the gas or ice giants.