Nauru Phosphate Royalties Trust

The Nauru Phosphate Royalties Trust (NPRT) was a sovereign wealth fund developed by the government of the Republic of Nauru in which the government invested money from the state-owned mining company, Nauru Phosphate Corporation. This money was then re-invested in a real estate portfolio, among other things, to provide the government with a reliable national income following the depletion of minable phosphates on the island.

Source: Wikipedia — Nauru Phosphate Royalties Trust (CC BY-SA 4.0)