Without any doubts, yumthang valley. I am an Italian traveler, been on road since two years, currently stuck in Jharkhand, India. I have been dreaming about Northeast for so long.
I visited sikkim 1 year ago, I must say it is one of the beautiful place I have ever visited. The nearby attraction you will get are lachung, yumthang valley, Tsomgo Lake, Baba mandir, nathula pass and so on. The best time to travel is November-January.
Hey! I loved the Tsongmo Lake, The Khangchendzonga National Park, the streets and weather of Gangtok and the Teesta River. Also, since my Uncle is in the Army, I had the privilege to visit Nathu La border and shake hands with a Chinese soldier. It was an amazing experience!
North Sikkim lachung (zero point ,yumthang ) and lachen (we didnt get to go due to heavy snow fall )
east sikkim tsmogo lake ,dont ever miss NATHULA PASS ,baba Mandir
South Sikkim -Namchi char dham ,Ravlanga ,Samdrupsta
west sikkim not visited