Tam Coc - 'Limestone karsts'
'This is what most travellers come to Ninh Binh to see: limestone karsts sweeping up from serene rice paddies, best appreciated on a languorous rowboat ride down the river, to the soundtrack of water lapping against the oars. It’s de rigueur to describe the area around Tam Coc as the inland version of Halong Bay, but that’s not exactly a fair comparison. Halong Bay sweeps across 3000 islands; at Tam Coc the encounter is much more intimate. Along a mere 2km of the Ngo Dong River, undisturbed by engine noise, the limestone outcrops loom closer, larger; this landscape would have suited the Romantic poets just fine.'
by Lonely Planet 'Vietnam'