This map shows the fort on the Island of Cobras, located in the harbor off the coast of Rio de Janeiro. The island was considered an important line of defense for the city of Rio de Janeiro and the approach to the colonial capital. The first fort was erected on the island in the 1620s, when Portugal’s Brazilian holdings were under threat from the Dutch as well as from the French and the English. Over the next century, the fort was rebuilt and expanded. Eventually, it included a house for the fort commander, a chapel, barracks, and storehouses for supplies. Cobras Island; Forts and fortifications