Depends on your preferences, if you love nature, The Famous Temi Tea gardens in the South, North Sikkim, of you can go in a mini trek, or if you prefer clubbing M.G market is the place for you. And dont forget the Plant Convervatory in Gangtok. They have many beautiful flowers and plants local to them and you can also go uphill and reach a waterfall.
Tsongmo and Gurudongmar lakes are serenity at their best. The later is one of the highest fresh water lakes in the world... I would say if you are in Sikkim for a week you must visit both, or at least one of them... Happy travelling Somya... --
Cheers,
@lifeoutsidecubicle
If you have taken a package from your travel agent you will get to see all the place but 1 place you wont get in package is kalaphatar which is in north sikkim
Must visit pelling. Incredible. Moreover in Sikkim, there is language problem although most people understand english. and must know the closing day of each spots. Drivers may not tell you the truth. You must get proper information from tourism offices.