Kauai (also known as The Garden Island) is an island on the planet Earth, part of the nation-state of Hawaii and the northernmost island of Hawaii's archipelago. Kauai is a beautiful location, attracting many tourists to such attractions as Ka'a Beach.
In the 22nd century, Jonathan Archer owned a condo on Kauai. Oan reminded him of the island. (ENT novel: Surak's Soul)
By the 23rd century, the Kauai government had taken steps to ensure that the beauty of the island's locations would remain unspoiled and natural. Kauai's capital was Lihue, the location of a shuttle field. Spock visited Kauai for a ten-day shore leave near Ka'a Beach in 2253, but was called away after four days, departing from the Lihue shuttle field. (TOS novel: Vulcan's Glory)