Don
Must see in Chengdu is the Panda Breeding Station...it is a very large and modern facility devoted entirely to the Panda. A lot to see and very interesting.
Many of the "Old Towns" surrounding Chengdu date back thousands of years when Chengdu was the Western Gateway into China. If you like ancient history, they are all fascinating.
There is also an archeological site where they excavated over 10,000 years of history, going back beyond the Stone Age. All the excavations have been "glassed over" and you can walk on them and look below. Several on-site museums display many , many artifacts in bone, jade, Gold and Silver...I cant remember it's name, but I will ask Ming tonight.
There is a huge market that has hundreds of small traders displaying antiques for sale. Many of them are fake, but some good bargains to be had.
And dont forget to have a genuine Sichuan hot-pot........the most fiery and tasty dish of all !!
Go to a tea house in a local Park by the river and pass a few relaxing hours and do some people watching !!!...with endless cups of delicious tea. The Mahjong crowd will have you in stiches with their antics...usually older people who dont work, they play all day for tiny money and have a riotous time and there are music groups who get together there just to practise tunes and singing......very beautiful, and peaceful even though it is in the heart of a busy City.
Cant help you with Mianyang...never been there !!