Pick any aircraft or satellite passing over your house right now, and go sit in its window seat.

The sky here is the real one outside — your location, your weather, this minute's light — with the aircraft and satellites that are genuinely overhead. Click one and the camera follows it; stow away and it takes a seat on board, over real terrain.

All of that is drawn in real time, which needs JavaScript and WebGL 2. Switching JavaScript on for this site should do it.