Which railway spans seven time zones and is so long that you can eat breakfast in Europe and dinner in Asia during the same journey?

What flows upstream in history but always runs north, through the heart of the desert? Solve the riddle → Its short borders enclose art treasures and an undeniable spiritual leader, in the heart of an eternal city. Solve the riddle → What was once criticized as an ugly construction, but is now an iron monument that breathes with the seasons? Solve the riddle → I am a colorful kingdom beneath the sea, built by tiny animals yet larger than many cities. What am I? Solve the riddle → What stretches like a spine across an entire continent, yet has neither life nor limbs? Solve the riddle →