Observation satellites used for different purposes orbited at different altitudes above the Earth's surface.
Weather and communications satellites were the highest, followed by resource survey satellites. Spy satellites, because they needed to see targets on the ground as clearly as possible, had the lowest orbits, only a little over a hundred kilometers above the surface. Since the upper boundary of the atmosphere was generally set at one hundred kilometers, no long-term satellite could orbit below that altitude.
But one did not necessarily need to be more than a hundred kilometers above the ground to overlook a place. There was a Ferris wheel in Place de la Concorde, modeled after the London Eye. However, because Paris residents felt it spoiled the cityscape and strongly demanded its removal, it was usually dragged out and operated only during winter.
It was like a temporary amusement park, something only children would ride. When Alessandro found Yang and his son, the two were having a great time on the Ferris wheel. Seeing Alessandro on the ground, Felix even waved at him from above.
Only after they had enjoyed themselves enough did Alessandro walk over and show them the golden incense boat he had acquired.
"They should be part of a set," Alessandro said. "There should be a thurible nearby."
"I know, one of those things with an incense burner hanging from chains that follows behind the chief celebrant, right?" Haji said.
"That's right, and we believe it's to the east." Alessandro raised his phone. "The Alps produce a kind of platinum salt. Two hundred and fifty million years ago, the Alps were beneath the sea. Lion Henry once tore down a bridge and forced a change in the salt route."
"So which city?" Felix asked.
"Strasbourg. They also drew some sort of diagram related to