Final answer:
The Ciudadela, a vast sunken plaza surrounded by temple platforms, is characteristic of Teotihuacan's plan that distinguishes it from other Mesoamerican cities.
Step-by-step explanation:
The characteristic of the plan of Teotihuacan that distinguishes it from other Mesoamerican cities is the presence of a vast sunken plaza called the Ciudadela. This plaza is surrounded by temple platforms and could accommodate an assembly of more than 60,000 people. The focal point of the Ciudadela is the pyramidal Temple of the Feathered Serpent, which exhibits the characteristic Teotihuacan architectural style.