There are two main routes through Sichuan to Lhasa, a northern route and a southern route. Both routes take an superlative scenery. The northern route offers a range of scenery from forested alpine country to the high plateau of the Changtang and passes many large monasteries; the southern route is lower, wilder and more alpine, passing fewer towns and monasteries and stunning lakes.
The northern route to Lhasa starts from Chengdu and you will have a chance to see the Giant Panda from Wolong Nature Reserve, the Four girls' mountain peaks, overnight at Danba where you can visit Danba Ancient block towers in Suopo. And passes Donggu Natural Reserve to Bamei, about 20km north Bamei visit the famous Tangong Monastery and other monasteries around Luohuo and Ganzi. Drive to Derge Scripture Printing Press from Ganzi takes a long day but there are plenty of exciting excursions en route, you will see the pretty Yihun La-tso. From Derge you cross into Tibet proper over some wild passes to Chamdo, the biggest town in eastern tibet. From Chamdo you will take the Tibet western northern route to Lhasa by passing Riwoche, Sok, Nagqu.
The Southern route to Lhasa runs from Chengdu to Kangding by visiting Hailuogou Glacier first, then the highest city in sichuan Litang, visit Litang monastery, then drive down to Litang before climbing up into Tibet at Markham. Markham is the first town since into Tibet, from Markham countinuing over concertina passes to Dzogang and Pomda. From Pomda, join the Tibet western southern route to Lhasa via Rawok-tso, Pomi, Draksum-tso in Baiyi.
Another popular overland route to Tibet for travellers is from Yunnan. You can start from Kuning, Lijiang or futhur north Zhongdian. Starting from Kunming, visit the famous stone forest nearby, then go to Daili see the ancient Daili town and do 2-3hour boating at Erhailake. Lijiang is one of four ancient towns in China, from Lijiang to Zhongdian by see the Tiger Leaping Gorges, where you can start to do 2-3day trek. Zhongdian to Deqin it's a half day bus ride, see the holy Mt. Meili. Cross the Tibetan border from Yanjing, then another 111km to Markham join the Sichuan Southern route to Lhasa