Answer:
Here you go:
Distinct dynasties built different courses of boundary walls. They reach in total from Liaodong in the east to Lop Lake in the west, from the present-day Sino-Russian border in the north to the Tao River in the south, along an arc that roughly delineates the Mongolian steppe's boundary. The Great Wall's protective system is now widely regarded as one of history's most spectacular architectural marvels.
Hope this helps.
Completely unrelated, but that is a great sentence, I want that painted as a quote on my wall.
Also, the punctiation seems right to me. But you might be able to use a ";" instead of a comma, im gonna check that real quick.
You shouldn't take regular breaks while working on a project.