Tesso Nilo National Park is a national park in Riau Province, Sumatra, Indonesia. It was declared a national park by the Indonesian government in 2004. The original area of the park was 385.76 km2, but the decision has been made to expand it to 1000 km2. Tesso Nilo National Park houses some of the largest coherent lowland rainforests remaining on Sumatra. The Center for Biodiversity Management has surveyed over 1,800 plots in tropical forests around the world. They found that no other plot has as many vascular plants as in Tesso Nilo