Ban, who is the first UN head to visit Bulgaria after the end of the communist regime in 1989, delivered a lecture entitled "The World in the Next 20 Years" hosted by the Atlantic Club in Bulgaria and Sofia University "St. Kliment Ohridski."
He opened the lecture by praising the Bulgarian tradition of tolerance and saying he is impressed with Bulgarian history.
"Future can come easier than we are expecting it. This means that what we foresee happening in 20 years might in fact happen a lot earlier, and this depends on us," the UN head stated outlining climate change and the shortage of food and energy, and poverty as major global challenges.
Ban urged the people around the world to "think big" by pointing out that even though the population of the earth continues to grow steadily, current political goals say that by 2050 the global output of greenhouse gases must be reduced by 50%.
"When I think about what we want the world to look like in 20 years, is that just and sustainable? We are setting a very dangerous path of development. We must find a more balanced way of harmony and growth," the UN chief said noting that some 70 million children globally do not attend school.
He outlined three big challenges referring to the Organization of the United Nations as well - achieving a more prosperous world without abject poverty, achieving a greener and cleaner world, and achieving a world without nuclear threats.
Ban explained that he is calling a global nuclear safety summit to take place in September 2011.
"More and more governments are beginning to realize that nuclear weapons create an illusion of security," said the UN Secretary-General while urging the individual countries to carry out complete reviews of their nuclear safety standards together with respective international efforts.
In his words, the International Atomic Energy Agency needs to play a bigger role in that respect.
"The costs and benefits of using nuclear energy must be thoroughly analyzed. What will happen if nuclear technologies end up in the hands of terrorists? Think about the tragedy in the Fukushima nuclear power plant in Japan. It must focus our attention on this topic," Ban Ki-moon declared in his lecture.
Regarding the civil unrest in the Arab world, Ban described them as revolutions creating opportunities that appear only once in the life of each generation. He further said the sending of UN peace-keepers in Southern Sudan, which recently declared independence, is under discussion.
The UN Secretary-General completed his Bulgarian lecture the way he started it - with a quote from Bulgarian national hero Vasil Levski about brotherhood regardless of ethnic, religious, and cultural differences.
"This is our challenge. This is our future," Ban concluded.