Konstantinos Apostolos Doxiadis was a man who had a really big brain and thought a lot about how cities work. He came up with a special way of looking at cities called "Ekistics".
Think of a city like a big puzzle with lots of different pieces that need to fit together just right. Konstantinos Doxiadis was really interested in making sure all the pieces of the puzzle fit together in a way that made cities work better for people.
He also thought about things like how to build cities so that they help people live better, like making sure there are enough parks and open spaces for people to enjoy being outside.
Basically, Konstantinos Doxiadis was a very smart man who thought a lot about how to make cities work better for everyone who lives in them.