Best Season to Visit : April - August and October - November.
Area :  31 sq km
Distance : 26 km from Gangtok
Altitude : 3350 m
It is situated around the area adjoining the Tsomgo (Changu) lake along the Nathula Road. Sanctuary abounds in alpine flowers like Poppies, Primulas and Rhododendron. Musk Deer, Serow, Himalayan Black Bear, Red Panda, Lesser Cats, Blood Pheasant, Satyr Tragopan, Impeyan Pheasant are some of the species found. This floristic sanctuary has a breath-taking variety of flowers between May and August. 

The earliest to flower are the different species of Rhododendron, though they each have slightly varied timings of peak flowering. In the open areas, you can see a flowering succession of variously coloured primulas, blue poppies, and Clematis in June; purple irises, pale yellow poppies (Meronopsis paniculata) and Friti1laria together with the little local strawberry Fragaria dotting the ground in July. The season ends in August in a blaze of golden senecios and bright purplish-pink Pedicularis siphonantha. The last to flower is Polygonum which covers the landscape, after which the area awaits its first snowfall. 

Many rare and highly endangered plants, some of great medicinal value are found here such as Podophyllum emodii, Aconitum spp. and Nardostachys grandiflora. The orchid Cypripedium elegans in particular is endemic to this area. Some solemn, majestic silver firs, Abies densa, stand sentinel over the area towering above the thickets of rhododendron and fields of tiny flowering plants. There are also dense bushes of bamboos at the lower altitudes, mostly belonging to the genus Arundinaria which forms an ideal habitat for animals like the Red Panda, Ailurus fulgens that thrive on their shoots. These bushes also play an important role in soil conservation. 

Bird life is represented by different types of laughing thrushes in shrubs and on the forest floor; the ubiquitous blue whistling thrush, redstarts and forktails near waterfalls and hill-streams; mixed hunting parties comprising small species such as warblers, tit-babblers, tree-creepers, white-eyes, wrens, rose finches, yellow- bellied fantail flycatchers, minlas and yuh~nas in rhododendrons and silver firs; raptors such as black eagle, blackwinged kite and kestrel patrolling the skies and pheasants such as monals and blood pheasant, now becoming rare. Many migratory birds also use Kyongnosla Alpine Sanctuary as a stopover before going down to the Indian plains or back to Siberia. 

Animals, though present are very difficult to spot during a casual visit; but as this is the only safe refuge available to them from the disturbance of nearby army cantonments, you may expect to see signs of musk deer, serow, goral, common langur and the red panda in the higher ranges of the sanctuary. There are records of leopard and black bear too. So look carefully for animal tracks and signs such as pugmarks, browsed branches, droppings, small trails and dens in rocks and tree snags. The forest will then come alive for you and with practice you will soon be able to identify the animal making these signs. 

Animals and birds breed late at this altitude sometime between May to August. A lot of the smaller species use underground dens and nests or lake over abandoned or disused burrows. It is not uncommon to find small rivulets formed from melting ;now of the winter months. Often the dense rhododendron bushes around these water bodies serve is ideal sites for nesting of birds and you should be careful not to disturb the hidden occupants by avoiding walking into these bushes. Do study elements of this unique high altitude lake ecosystem.