"Do you see the river next to the mountain?"

Translation: Βλέπεις το ποτάμι δίπλα στο βουνό;

[fazulakis]

perhaps "βλέπετε" should be added?

[jaye16]

Good catch. It's been added. Thank you.

[Isidor868839]

Why is δίπλα από το βουνό wrong?

[jaye16]

Because the correct collocation is "δίπλα στο". "Από" would be "from".

[VukSamac]

Why not πλάι instead of dipla?

[G.Georgopoulos]

That, too, added now.