In 610 CE, Muslims believe that the Prophet Muhammad had a profound spiritual experience in a cave on Mount Hira, located outside Mecca. During this event, he was visited by the angel Gabriel (Jibril in Arabic), who commanded him to recite messages that were to be revealed to him by Allah (God). This moment marks the beginning of Muhammad's prophethood and the revelation of the Quran.
The other events mentioned, such as the night journey and ascension to the heavens (Isra and Mi'raj), occurred later in Muhammad's life, and the Hijrah (migration) to Medina happened after he faced persecution in Mecca. Thus, the key event that happened in the cave in 610 CE is the first revelation received from Allah through the angel Gabriel.