Final answer:
The ancient Greek structure described as a detached portico used as a promenade or meeting place is known as a Stoa.
Step-by-step explanation:
The ancient Greek structure known for being a portico used as a promenade or meeting place around public areas is known as a Stoa. This feature was typically detached and of considerable length, providing a space where people could gather, converse, and appreciate public activities. Notable ancient Greek architectural sites like the Acropolis contain various examples of stoas, which are distinguished from other features such as the Erechtheion with its caryatids, the Propylaea, and temples like the Parthenon that feature Ionic colonnades and were planned by architects like Iktinos and Kallikrates.