Located in Ninh Binh province, the Tam Coc caves are known as the inland Ha Long bay. It is 3 hours drive out of Hanoi. At the river docks, you board an open-air sampan which you hire with a rower. The boat ride takes you through a winding waterway which passes through 3 caves (Tam Coc).You must actually duck a bit as the boat does through the caves to avoid scraping the roof. Look out also that you do not hit any of those stalactites or stalagmites!
On the last of these caves, a group of traders on sampans will try to sell you drinks and tit-bits. Some actually ask you to buy a drink or two for the rower only that the rower will not actually drink it, she'll most likely trade it back later on.
The rower will also likely try to sell you embroideries and paintings. Bargain abit, buy some if you fancy. But if they pester you too much, you can actually note down the boat number and lodge a complaint at the tourist police office at the dock. My experience was the rowers are quite nice and they don't create any trouble.
The village at the dock has many stalls selling T-shirts and other kind of hand-made linen. Prices are quite cheap. There are also restaurants and cafes. The specialty here is baked mutton wrapped in rice paper!