Translation:On the map there are as many rivers as there are mountains.
Is THERE needed in this sentence? I was marked wrong with: On the map are as many rivers, as mountains.
Huh...as a native speaker I feel like while it's antiquated, it's basically fine to leave out the "there," (Although the comma is definitely wrong.)
If I were making the call I'd probably accept "On the map are as many rivers as mountains." if you're willing to say it while dressed in Wise Old Mentor robes in between other cryptic advice.