One quote called Olhão "the town of many faces." It is a fishing village with bayfront produce/fish markets in the heart of town. The pedestrian cobblestone streets in the heart of Old Town are a highlight, as is the palm-lined promenade along the bay. We used it as a base to explore the nearby town of Tavira, which had a castle, historic churches and town squares, and salinas (salt production), and to explore nearby Spain.
This picture of Olhão market was taken from the boat we took to Ria Formosa Park (gorgeous!) and Culatra. An enterprising boat owner approached us on the street in front of the market, and offered us a nice tour package.
Our favorite restaurant was Casa De Pasto Algarve. It is family-run and we felt so much at home there, in addition to loving the food.
Olhão is a bit gritty in spots and you will need a car to best get around, but I loved getting a feel for the locals' Algarve.