This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Although the rivers and coast of this area were among the first places colonized by the Portuguese, who set up trading posts in the 16th century, they did not explore the interior until the 19th century. The local African rulers in Guinea, some of whom prospered greatly from the slave trade, controlled the inland trade and did not allow the Europeans into the interior. They kept them in the fortified coastal settlements where the trading took place. African communities that fought back against slave traders also distrusted European adventurers and would-be settlers. The Portuguese in Guinea were largely restricted to the port of Bissau and Cacheu. A small number of European settlers established isolated farms along Bissau's inland rivers.
What areas were the first places colonized by the Portuguese?