"I had left my heart in Delhi. I am returning regularly to check whether half of my heart is totally functioning," he said delivering a lecture at the Indian Council of World Affairs.
Ban worked in South Korean Embassy as vice consul which was his first overseas posting after joining foreign service.
"I am happy to be in New Delhi... Mei Bharat wapas ake bahut khush hoon," he said, adding "I started from here 43 years ago in 1972."
His current visit is fourth to India as UN Secretary General.
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Ban was the foreign minister of South Korea from January 2004 to November 2006. On October 13, 2006, he was elected the eighth Secretary-General of the United Nations.
On June 21, 2011, he was unanimously re-elected by the General Assembly to the top post. He continues in his post till December 2016.
Ban had arrived here on Saturday on a four-day visit. He had also attended the Vibrant Gujarat Summit in Gandhinagar.