Explain any three importance of  passes to spread out the indian culture and trade ?

Following are the three importance of passes in the Indian culture:

• The various passes across the mountains in the north have provided passages to the ancient travellers, while the
  oceans restricted such interaction for a long time.
• These routes have contributed in the exchange of ideas and commodities since ancient times. 
•  The spices, muslin and other merchandise were taken from India to different countries.