The Sri Lankan variety of montane rain forests are found in few places within central highlands like Horton Plains, Knuckles Range and Sri Pada Range (Peak Wilderness). Usually these forests can be seen in mountain tops above 4500 feet from sea level. Below that level we find another type known as sub-montane forests.
Montane rain forests have thick undergrowth and it is extremely difficult to walk across a forest patch. Due to the cold weather and high winds the trees in these forests are not that tall compared to the rain forests in lowlands. Trees are usually around 20-30 feet tall and there is a low canopy. Sub-montane rain forests are a transitional stage between the lowland and highland vegetation. Both these forest types are high in biodiversity. Another interesting feature is cloud forests, which I have experienced quite a lot while hiking in these forests.
Above picture, taken from Sri Pada Range shows part of the montane rain forest there. More photos in this link show both high montane as well as sub-montane rain forests.