Thiladhunmathi was the biggest administrative area of Maldives, consisting of Haa Alif Atoll and Haa Dhaalu Atoll. Sometimes it is called as Boduthiladhunmathi, which includes part of Shaviyani Atoll.
Map of Thiladunmath%C3%AD, Maldives
References
Thiladhunmathi Wikipedia(Text) CC BY-SA