Jupiter
My exploration of space began with marveling over Jupiter. I still can't wrap my mind around the fact that the designer of this planet (which has a radius of 43,400 miles) cares about me. Whether or not you're on board with creationism, I think we can all at least agree to be mind blown by the greatness of Jupiter. If you were to combine the mass of all the other planets in our solar system, Jupiter would still be about 2.5 times that mass.