is the mentioned place a country?
Yes, an independent country.
Kiribati
Kiribati (), officially the Republic of Kiribati (Gilbertese: "[Ribaberiki] Kiribati"), is an independent country in the central Pacific Ocean. 
when was caroline island sighted for the first time? 1606 who did that? Europeans what is the island's location? It is the easternmost of the uninhabited coral atolls which comprise the southern Line Islands in the central Pacific Ocean of Kiribati.
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Kiribati [SEP] Introduction
Kiribati (), officially the Republic of Kiribati (Gilbertese: "[Ribaberiki] Kiribati"), is an independent country in the central Pacific Ocean. The permanent population is just over 110,000 (2015), more than half of whom live on Tarawa atoll. The state comprises 32 atolls and one raised coral island, Banaba. They have a total land area of and are dispersed over . Their spread straddles the equator and the 180th meridian, although the International Date Line goes round Kiribati and swings far to the east, almost reaching the 150° W meridian. This brings Kiribati's easternmost islands, the southern Line Islands south of Hawaii, into the same day as the Gilbert Islands and places them in the most advanced time zone on Earth: .