For those who would like to get away from the bustle and hustle of the big cities like Hanoi and interested in outdoor activities such as trekking, sampan boat-riding, cruising in the beautiful landscape, this is the one. With 4 days, start with a scenic drive to the mountainous province of Hoa Binh, the scenery is getting more and more beautiful, specially the stop for viewing over Mai Chau will give you a great start. Get insight into the Thai ethic group culture on the afternoon trek to villages, fruit gardens, rice fields...
Once you are in Ninh Binh, admire the mythical beauty of Trang An Scenic Landscape from a sampan boat, rowed by a local farmer, taking you through many tiny limestone caves. This is really worth the 3-hour row.
The trip will finish with a relaxing cruise on Halong Bay, one of the seven world wonders. With an overnight cruise, you definitely understand why the bay is recognized as the World Heritage twice by UNESCO.