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Mountain Jabal al noor
The Prophet (PBUH) after a series of dreams went to the moutain where he found the cave. In which he was revealed as the messenger of ALLAH(swt). He had spent a month in the cave of which is where the first revelation was revealed and the month became ramadan.
From that month Islam was born and grew larger and larger and is still growing today. I would say that mountain Jabal al noor is where islam grew to beome what is it today a universal religion with many ethicities and diversity.