Who was a Greek city planner that devised a scheme to organize Athens in rectangular blocks?

The correct answer is Hippodamus.

Hippodamus of Miletus was a famous ancient Greek architect, as well as scientist. He is now considered to be 'the father of European urban planning' because of his contributions to Athens. He was the one who decided it would be for the best to organize Athens in rectangular blocks, rather than build it in some other way. He valued order, in architecture, as well as in life and politics, which can be seen in his designs.

Hippodamus is the answer. He was a Greek city planner that had a scheme in organizing Athens via rectangular blocks. However it was different as the rectangular scheme would then allow the invaders to get inside easily. Hope this is the answer.