Marintrylla (trollish name: Weeriiduulooaa) is the trollish capital city, an island near New Zealand. It is described as an intricate network of caves and bridges. As we know of, none of the characters have visited the city itself yet. Tarina said in Flashback that there is somewhere there that they can access the troll hive. It was first mentioned by name in Legacy when Sophie visited Mr. Forkle’s office.
Marintrylla: Little is known about Marintrylla, since elves are rarely invited to visit. But the city serves as the trollish capital and includes Empress Pernille's palace. Marintrylla is housed on a secret island and consists of an intricate network of caves and bridges - and it should be noted the city likely doesn't include on of the Trolls' special hives. Those appear to be hidden among elvin locations, thanks to Luzia Vacker (who secretly served as an ally to one of the trollish empresses), in order to keep the trolls' unborn babies safe from ogres. They are most likely covered in illusions.