Rio Grande do Norte is known for the beauty of beaches such as Forte, Pipa, Genipabu and Redinha, with crystal clear waters, dunes and reefs. Its cultural wealth is historical. Taking just the city of Natal: it was a refuge for French privateers and Dutch pirates, a destination for European Jews fleeing religious persecution, and an American military base during World War II. There the Portuguese built the Fortaleza dos Reis Magos, at the mouth of the Potengi River, in the 17th century.