Which archipelago was the site of a successful campaign against malaria led by the German physician and microbiologist Robert Koch in 1901?

The Brijuni (Brioni) Archipelago in the northern Adriatic Sea (off Istria, today Croatia) was the site of a successful anti-malaria campaign led by Robert Koch around 1900-1902.

At the time, the islands were heavily affected by malaria due to mosquitoes breeding in marshes and ponds, which had made earlier settlement and tourism projects difficult. Koch implemented a practical control strategy: draining or filling standing water where mosquitoes bred and treating infected people with quinine.

The campaign worked, and malaria was effectively eliminated. This allowed industrialist Paul Kupelwieser's planned luxury health resort to develop on the islands.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9242531/