Ibn 'Umar (May Allah be pleased with them) reported:
Whenever the Prophet (ﷺ) and his army ascended a height, they would proclaim: "Allahu Akbar (Allah is Greatest)," and when they climbed down, they would proclaim: "Subhan Allah (Allah is free from imperfection)."[Abu Dawud].
App reference: Book 8, Hadith 21
Arabic/English book reference: Book 8, Hadith 976