Just outside of Ninh Binh there are series of lookout points and caves that take advantage of the surrounding karst landscape as the cliffs loom impossibly steeply out from the flat lush valley floor. The Huang Mua area has a tourist spot where you can climb up one of the hills and get great views around the UNESCO World Heritage listed landscape. Plus just to the west there are some small roads that allow you to cycle through the area.
It gets close to that classic picture-perfect karst towers view, but overall its a little touristy and, if you have the choice, head further inland. Only a few hours away to the north west is Mai Chau – far more atmospheric and less touristy. Definitely worth the extra drive and for tips and highlights see Cycling through the patchwork rice fields of Mai Chau.
And for ideas on how a trip to Tam Coc or Mai Chau can fit into an itinerary for experiencing the highlights of Vietnam, see this entry A 3 week itinerary for the highlights of Vietnam.