Shadow Cay was ostensibly an island in the Caribbean near Cuba. It was really a Sycorax spaceship disguised as an island after the wives of the tribe that invaded Earth in 2006 went looking for their missing husbands.
It was equipped with a magma-sculptor that shaped it to look more like a Caribbean island, and also created a copy of Westminster Abbey called the Church of the Sycorax as a shrine to where Fadros Pallujikaa fell to his death. The Sycorax widows hypnotised all of humanity to believe the island was discovered by Columbus in 1492 and home to a Tiano tribe, and that the abbey was a convent built in 1823.
In 2009, the ship's magma-sculptor was overloaded by the Tenth Doctor, who made it copy and recreate the whole of the Earth, and set its controls to take off before it exploded. (COMIC: The Widow's Curse)