Variantly, "mountains and plains": The flavor of the fruits of a mountain is not similar to that of the fruits of a plain. This tells me only of the fruits of a mountain vis-à-vis those of a plain. Whence do I derive that the flavor of the fruits of one mountain is not like that of another and that the flavor of the fruits of one plain is not like that of another? From "a land of mountains (plural) and plains" (plural) — many mountains, many plains.
R. Shimon b. Yochai says: Twelve lands were given (to Israel) corresponding to the twelve tribes of Israel, and the flavor of the fruits of one land were not similar to that of each of the others. And these are the (twelve) lands: (Devarim 8:8) "a land of olive-oil and honey," (Bamidbar 14:24) "I shall bring him (Calev) to the land whence he came," (Devarim 4:14) "the land whither you are crossing to inherit it," (Ibid. 11:11) "a land of mountains and plains … (Ibid. 12) a land which the L-rd your G-d inquires after," (Ibid. 8:7) "For the L-rd your G-d is bringing you to a good land, a land of streams of water … (Ibid. 8) a land of wheat and barley … a land of olive-oil and honey (Ibid. 9) a land where not in constraint shall you eat bread … a land whose stones are iron … (Ibid. 10) for the good land" — twelve lands corresponding to twelve tribes. And whence is it derived that the flavor of the fruits of one tribe were not similar to that of another? From "a land of mountains (plural) and plains" (plural) — many mountains, many plains, (each unique in itself).