Siman 228
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א עַל יַמִּים וּנְהָרוֹת, הָרִים וּגְבָעוֹת וּמִדְבָּרִיוֹת, אוֹמֵר: בָּרוּךְ אַתָּה ה' אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם עוֹשֶׂה מַעֲשֵׂה בְרֵאשִׁית; וְעַל הַיָּם הַגָּדוֹל, וְהוּא הַיָּם שֶׁעוֹבְרִים בּוֹ לְאֶרֶץ יִשְׂרָאֵל וּלְמִצְרַיִם, אוֹמְרִים: בָּרוּךְ אַתָּה ה' אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם עוֹשֶׂה הַיָּם הַגָּדוֹל.
1 Upon oceans, rivers, hills, mountains, and deserts one says, "Blessed are you, God our Lord, king of the world, creator of the original (first) creations." And upon the great ocean, and that is the ocean that is crossed to Israel and to Egypt one says, "Blessed are you, God our Lord, king of the world, creator of the great ocean."
ב לֹא עַל כָּל הַנְּהָרוֹת מְבָרֵךְ, אֶלָּא עַל אַרְבַּע נְהָרוֹת דִּכְתִיבֵי בַּקְּרָא, כְּמוֹ חִדֶּקֶל וּפְרָת (בְּרֵאשִׁית ב, יד) וְהוּא שֶׁרָאָה אוֹתָם בְּמָקוֹם שֶׁלֹּא נִּשְׁתַּנָּה מַהֲלָכָם עַל יְדֵי אָדָם.
2 Not on every river should you recite the blessing, but rather on the 4 rivers, as it is written "like Chidekel and Euphrates." And he who saw them in a place that wasn't normally walked by people.
ג וְלֹא עַל כָּל הָרִים וּגְבָעוֹת מְבָרֵךְ, אֶלָּא דַּוְקָא עַל הָרִים וּגְבָעוֹת הַמְשֻׁנִּים, וְנִכֶּרֶת גְּבוּרַת הַבּוֹרֵא בָּהֶם.
3 And not on every hill and mountain should you recite the blessing, but rather only on hills and mountains that stand out as recognizably great and awe-inspiring.