Lets be honest here - not many travellers spend much time in north central Vietnam primarily because, well, it's not exactly overflowing with attractions - of course for some, that's an attraction in itself, but for the rest of us, ie just about all of us, this region is little more than a blur out of a train or bus window.
Nevertheless, this region of Vietnam stretches for more than 300km, from Ninh Binh in the north to the Demilitarised Zone to the south, and if it's your mission in life to tick off absolutely everything Vietnam has to offer, then you'll be needing to spend some time wandering around this part of the country.
Working from north to south, a visit or Vietnam tours to Tam Coc near Ninh Binh should be on anybody's shortlist and the massive Phong Nha - Quang Binh caverns down at the southern central vietnam end in Dong Hoi province are absolutely amazing - really! Between the two, you'll find a lot of very hospitable people, curiously wondering what on earth you're doing in their home town, be it Ha Tinh, Thanh Hoa or Vinh. Chances are, while you'll find few distractions worthy of a scrapbook entry, you will, in all likelihood meet a lot more local people than you will in Hue, Nha Trang and Hoi An - and that's what travelling is all about right?
Another reason why you may find yourself in the region is because there's a couple of overland routes from Laos to Vietnam that empty out in this part of the country - you'll most likely find yourself deposited in Thanh Hoa of Vinh - both of which are more than adequate for an overnight stay before moving on to other, more interesting parts of the country.
Nevertheless, if you're after remote, un-touristed Vietnam, you're in the right place.