Final answer:
The term used to describe a grand entrance or doorway is a 'Portico', which is a large porch with columns and a roof structure that leads to the entrance of a building.
Step-by-step explanation:
The term used to describe a doorway, gate, or entrance that is imposing and emphasized by size and stately architectural treatment is a Portico. A portico is typically a large porch leading to the entrance of a building, often with columns and a roof structure. For instance, one approaches the Pantheon through the portico with its tall, monolithic Corinthian columns. Similarly, the Cathedral of Notre Dame de Chartres features a Royal portal, which is an elaborate, architecturally significant entrance. These architectural features not only add to the grandeur and elegance of the structures but also convey a sense of importance and power.