An-Nahl 16:15
The verse gathers three elements in the same sentence: rawāsī (firm mountains), anhār (rivers), subul (paths).
وَأَلْقَىٰ فِى ٱلْأَرْضِ رَوَٰسِىَ أَن تَمِيدَ بِكُمْ وَأَنْهَـٰرًا وَسُبُلًا لَّعَلَّكُمْ تَهْتَدُونَ
And he cast mountains on the earth, lest it shifts with you; and rivers, and roads, so that you may be guided
An-Nahl 16:15 · Translation: talal-itani
Image
Three distinct layers: stability, flow, passage. At the end of all of them, a single aim: "laʿallakum tahtadūn" — that you may find the way.
Observation
In geography the three form an inseparable chain: mountain ranges concentrate precipitation, melting snow and rainfall feed the river basins, and rivers over time cut valleys and natural routes of passage. The world's settlement map is largely laid out at the intersection of these three elements — cities most often arise on the side of a river, at the foot of a mountain, at the crossing of a road. The verse describes not three separate phenomena but a landscape in which they are interlaced.
Exegesis
Classical exegetes give particular weight to the verse's closing: "tahtadūn" carries both the physical sense of finding one's way and the spiritual sense of guidance. Al-Zamakhsharī (al-Kashshāf) notes that the verse draws upon both readings sitting one atop the other: the paths of the outer world can be a doorway to understanding the path of the inner. Ibn Kathīr draws attention to the verb "alqā" ("to cast") used of the mountains — as of an element later added to the earth, placed into position.
Sources
Tafsīr: al-Zamakhsharī · al-Kashshāf; Ibn Kathīr · Tafsīr al-Qurʾān al-ʿAẓīm. Science: hydrology — the mountain-river-basin relationship; literature on historical geography and settlement patterns.