Terceira also referred to as the “Ilha Lilás” (the “lilac” or “violet” island), is an island in the Azores archipelago, in the middle of the North Atlantic Ocean. It is one of the larger islands of the archipelago, with a population of 56,000 inhabitants in an area of approximately 396.75 km². It is the location of the historical capital of the archipelago, the Azores' oldest city and UNESCO Heritage Site (Angra do Heroísmo), the seat of the judicial system (Supreme Court), main base of the Azores Air Zone Command (Commando da Zona Aérea dos Açores) Base Aérea nº 4 and to a United States
Air Force detachment.
A small number of Hypogea (earthen structures carved into rocks, that were used for burials) were discovered on the island of Terceira, indicating a history of settlement that may date back 2000 years, and alluding to a presence on the island before the Portuguese.
The western part of Terceira Island is more heavily forested than the eastern part, due to the prevailing westerly winds bringing increased precipitation to that side, resulting in forests of Cryptomeria (Cryptomeria japonica).The northern coast is an area marked by evidence of volcanic activity with several "mistérios" (lava fields), the swimming pools of Biscoitos, while the centre of the island is highlighted by the Algar do Carvão and Furnas do Enxofre (dormant and active volcanic forms) that are popular with tourists and geologists.