Chiang Mai is Thailand's second city.  It was once the capital of the Lanna Kingdom. Many who come here usually return again and again, or stay for months or even years. Chiang Mai has a huge number of places to go and things to do in the way of temple visits, street food, adventure, nature, shopping, culture and nightlife!
During your visit, you might try these activities and places nearby the city:

Wat Phra That Doi Suthep/ Hmong Village(Doi Pui)
The most famous attraction in all of Chiang Mai is Doi Suthep. It is apparently the landmark of the city. Wat Phra That Doi Suthep, a 13th century temple,  is about 13 km from the city center and it also has a fantastic view over all of the city. There is also a famous Hmong village where you can visit and buy handmade products.
 
More info: http://www.chiangmai.bangkok.com/attractions/doi-suthep.htm

Wat Chedi Luang / Wat Prasingh
There are many temples in the old city buy these two are very attractive. Both temples are located in the old city and very close to each other. Wat Chedi Luang is the ruins of an ancient temple situated in the center of Chaing Mai. The temple is still an active worship place so you will still see monks as well as several Buddha shrines.  Wat Phra Sing is a Buddhist temple and monastery that was founded in the 14th century.  The temple of the Lion Buddha is an active temple.  Hundreds of monks and novices are still living there. There is a number of highly revered and very old Buddha images.
 
More info: http://www.chiangmai.bangkok.com/attractions/wat-chedi-luang.htm

Elephant Nature Park / The Long Neck Karen Tribe / Tiger Kingdom
Mae Rim district consists of many famous tourist attractions. These tourist attractions are just some interesting in the district which takes less than an hour to get there. The district also is ideal for those looking some more extreme sports and outdoor adventure.
   
More info: http://www.chiangmai.bangkok.com/attractions/mae-rim.htm

Saturday Night Market / Sunday Walking Street
Shop till you drop! Two different locations. The Saturday Market (Wui Lai Market) is located opposite the Chiang Mai Gate. The Saturday Market extends about 1 km all along the Wui Lai Road.
If you miss the first, there is the one on Sunday which however is much bigger.  The Sunday Market or the Walking Street Market is the most famous of all the markets in Chiang Mai, it opens every Sunday evening starting at Tha Pae Gate and running along the entire length of the Ratchadamnoen Road. There are plenty of handmade goods and foods as well as Lanna music events and temples.
  
More info: http://www.chiangmai.bangkok.com/shopping/weekend-walking-streets.htm

 

Night Bazaar
The Night Bazaar is approximately 1 km long on Chang Khlan Road which is not far from Tha Pae Gate. The Night Bazaar is open every day of the year from dusk till around midnight.

More info: http://www.chiangmai.bangkok.com/shopping/night-bazaar.htm

Nimman Road 
Trendy area with boutiques, cafes, bars, restaurants and galleries.  Nimmanhaemin Road is one of busiest part of Chiang Mai. It is the place where all people of the area hang out. There are shopping malls which contain many designer shops as well as a multiplex cinema and many famous restaurants.
 

More info: http://www.chiangmai.bangkok.com/nimmanhemin/

 

Chiang Mai Night Safari
A spectacular sight to enjoy for everyone, it is considered the most beautiful Night Safari in the world. There are great shows with a variety of wild life. Seeing the animals during the night is quite a fun experience. It takes just 30 min from the city.

More info: http://www.chiangmai.bangkok.com/attractions/night-safari.htm