Seychelles

 was an island nation on Earth. Polly Wright once travelled there with at least her father before she met the First Doctor. It was likely the first major international trip she took, as she went there on a brand new passport. (MA: Invasion of the Cat-People) It was also the first place to which the Eighth Doctor brought Samantha Jones in the TARDIS. Thanks to her performance in the effort against a Rhiptogan invasion on the Seychelles' Silhouette Island, he allowed her to continue travelling with him. (AG: Bounty)