Question

the worlds largest capital city and the country where it is located

Answer 1

That depends upon whether you're considering just the population within the city limits or the entire metro area. Many sources say the largest capital city is Tokyo, Japan.

However, you'll find the comparative populations within city limits here. This site names a Spanish-speaking capital as the largest.

http://www.infoplease.com/ipa/A0855603.html#axzz0yyaflVvy

Answer 2

It keep changing and depends upon whether you mean "largest" in population or area, and whether you count the entire metropolitan area. It also depends upon whether you consider Tokyo to be the capital of Japan. According to tradition and some written documents, Japan's capital is Kyoto. In actuality it is not.

The answer you are probably seeking, since this is a Spanish question, is Mexico City. Sao Paulo, Brazil was almost as large at last count.

Tokyo is larger than either of them.