Aryabhatta, the great astronomer and scientist, discovered zero. The number system was also invented in ancient India. - It was during the 6th century that Budhayana first calculated the value of pie and explained the concept of Pythagoras theorem. - The oldest city in the world that is still inhabited today is Varanasi. - Mawsynram, a village on the Khasi Hills, Meghalaya, receives the highest recorded average rainfall in the world. Cherrapunji, also a part of Meghalaya, holds the record for the most rainfall in the calendar year of 1861.