You can finish touring all the principal sights of Yakutsk and the nearby areas in just 3-4 days. But there are a ton of activities especially outdoor activities beyond the city limits for the adventurous traveler. Travel agencies will help you set these up, and given that this is Russia, it may well be wise to plan your trips through one. Here are some ideas:
Warm water cruises along the Lena River to the Lena Pillars and back 2-3 days
Warm water cruises along the Lena River to the Northern Sea 14-15 days
Road trip to the Buluus glacier 1-2 days
Air travel to the unique spires/hoodoo rock formations of the Northern Mountains by Kisilyakh 5-7 days
Air travel to the Northern Sea by Tiksi 3-7 days
Road trip to Oymyakonâthe Northern Pole of Cold. The coldest place on earth outside Antarctica. No joke, it's a village who the heck decided to live here? with the lowest recorded terrestrial temperature in the Northern Hemisphere.
Trip to the reindeer farm at Magaras 150km, 1-2 days
Rafting along the Buotama River 5-10 days
Rafting along the Blue СинÑÑ River 7-10 days
Rafting along the Amga River 7-14 days
Winter trip to the Lena Pillars with ice fishing 1-2 days