This river cut through an existing crater, forming a lake, maybe, which gathered sediments, burying the bottom, making fossils. You can tell the river has not flowed for a long time by the craters which were obviously formed after the river cut its channel. People flock to New Hampshire's Old Man of the Mountain. Freely floating habitats In a Freely Floating habitat, you can recreate a small portion of the Earth's surface. But there is a whole lot more.
Weaker gravity is a short elevator ride away.
Solar Energy Energy is available continuously, and the only limit to the power you can use is the size of the mirror you can build. Building power stations, that beam the Solar ennergy down to earth, either as microwaves or infra-red lasers could supply cheep power to remote locations. Gravity decreases substantially as you go higher. In a cylindrical station, you could fly a bicycled powered airplane with no trouble. In a sphere, you could go up hill easily since gravity would be getting less.