Archeological remains confirm that Chiang Saen had been a crucial site of human settlement since pre-historic times.
This riverside town covers the area of approximately 500 acres, 36 of temples remain to mark the city boundary including old city walls, moats, fortresses. gateways, and temples.
Wat Chedi Luang
Built in 1291, this temple houses the biggest chedi in Chiang Saen. It is a bell-shaped chedi with an octagonal base. The main hall and other surrounding chedis have all fallen in ruins.
Chiang Saen National Museum
The museum arranges three displays for its visitors. The first Section narrates the settlement history of Chiang Saen and its pre-historic culture. Archeological finds on display comprise stucco Sculptures from Wat Pa Sak, Buddha images in Lanna artistic Style, ancient inscriptions, and pottery.
The second section of the museum mainly provides information concerning archeological sites and artifacts which had been unearthed in Chiang Saen.
The third part is the exhibition of ethnic people along the Mekong River basins, including Tai Yai, Tai Lue, and other hilltribe people. The museum is open on Wednesdays-Sundays from 8.30 am to 4.30 pm, except on official holidays. Admission 10 baht. Information about the ancient city of Chiang Saen is available at the tourist service center opposite the museum.
Wat Pa Sak
In 1295, Prince Saen Phu built this temple to contain Buddha’s relics. He also had 300 teak trees planted in the temple compound.
Wat Pa Sak sits on 16 acres of land. There are 22 historic remains on the temple grounds. The main bell-shaped chedi has five tapering spires. The chedi at Wat Pa Sak are considered to be in the best physical condition as well as the most beautiful of Lanna style. The pattern and design on the chedi reflect artistic development in Chiang Saen, revealing its original adoption of Sukhothai, Pagan (Phukam) and Hariphunchai artistic styles. Through the process of cultural transformation, a unique Chiang Saen style was realized. It has since become the prototype of Lanna chedis.
Admission to the temple is 10 baht.
Wat Phra Chao Lan Thong
Phraya Son Ratchada-ngoenkong had this temple built in 1489. He also had a huge Buddha image made. The dimensions of this image are 2 meters by 3 meters, using about 1,200 kilograms of gold. It was thus called Phra Chao Lan Thong, indicating the price of the gold used. Another beautiful image in this temple is Phra Chao Thong Thip. which is a Sukhothai styled bronze Buddha image with very beautiful facial features.
Wat Phra That Chom Kitti
This temple challenges its visitors to climb up 339 steps in order to admire its beauty. It is, however, also accessible by car. King Phangkharat had this shrine built to contain Buddha’s relics. In 1487, Muen Chiang Song had a new pagoda built to cover the old pagoda.
Another pagoda containing Buddha’s relics in the area is Phra That Chom Chaeng. A look-out point behind this pagoda offers a vantage point to enjoy the Mekong vista.
Wat Phra That Pha Ngao
Built uniquely on a big slab of solid rock. Phra That Pha Ngao is a relatively small bell-shaped pagoda. Another slab of rock stands in front of the pagoda as though it were the shadow. Thus derived the name pha-ngao, meaning the rock shadow. Initially, this temple was called Wat Sop Kham. Its former location was by the Mekong River, and the temple was annually eroded by the tides. Townspeople thus agreed to rebuild the temple further inland by a deserted temple at the foot of Doi Kham. During the construction, they found under the base of the old Buddha image a magnificent Chiang Saen style statuette in subduing mara posture. After half of the Buddha image was revealed. the excavation was stopped and a prayer hall was built to cover it. The image was called Luang Pho Pha Ngao.
Phra Borommathat Phutthanimit Chedi
This gigantic white chedi on top of Doi Kham was constructed as a meritorious donation to the present King Bhumibol and Queen Sirikit. This is another vantage point to enjoy the view of the entire city of Chiang Saen.
Chiang Saen Lake
Commonly known as Nong Bong Khai sanctuary since 1985, the lake covers about 640 acres of land. This is an exceptional sight, especially in the cold season when seas of mist cover the whole area. It is a much-chosen recreational resort for local people and tourists. Another special treat at this lake is several flocks of rare birds that migrate to settle around the lake in the cold season, especially audubons, mandarin ducks, teals, and several others.
One of the best known tourist attractions in the world, the Golden Triangle, is in Chiang Saen where the Mekong River enters Thailand. 
For an aerial glimpse of the Golden Triangle, you need to climb uphill to Doi Chiang Miang by the Mekong River where Wat Phra That Doi Phu Khao once stood. Only a pile of bricks remains to mark the site, but it provides a look-out point to catch the big picture of the Golden Triangle. 
Once a cash crop in this region, opium is now merely a subject of close scrutiny on display in this museum. Visitors will learn all about its history in the Golden Triangle. The museum is open from 8.00 am. to 06.00 pm. Admission is 20 baht. 
This border town faces Myanmar across the Mae Sai River, and is located 62 kilometres north of Chiang Rai on Highway No. 110. Numerous shopping opportunities exist for popular Thai and Burmese goods. 
About 100 meters before the Mae Sai border, there stands another important place of Chiang Rai called Wat Phra That Doi Wao. This chedi was built by a ruler of Yonok Nakkhaphan to contain some strands of Buddha’s hair. It is thus one of the most ancient and most worshipped chedis in Chiang Rai. From the vantage points at this temple, you can visit Myanmar by sight, without having to pay the fees or crossing the borders. 
This is another popular place of worship on Doi Mae Salong. 
Tea is Doi Mae Salongs cash crop exported as far as Bangkok and Taiwan. Tea plantations spread along the mountain terrains. The varieties grown here are both local and imported kinds. Tea shops on Doi Mae Salong allow tourists to have a pre-purchase taste of the tea. Other take-home products available include temperate fruits. preserved fruits, and Chinese ingredients. 
From early or the end of January is the time for the Thai variety of cherry blossoms (locally called Nang Phaya Sue-Khrong meaning tigress flowers). More than 4 kilometers of roadway on Doi Mae Salong are then decorated with pink blossoms. Tigress flowers belong to the same family as cherries, peaches and plums. They usually thrive on high grounds, about 1,000 – 2,000 meters above sea level.