When I was deciding about where I will go for the last trip in the north I didn't have many options because it was rainy, so the places I planned to see were flooded - Even though I have heard later on that they are just freaking out and actually nothing is really happening there, so next time I will go even if there are "floods". The place I finally chose was called Ninh Binh.
I went again with the same agency as to the Ha Long Bay organized by my hotel. It was a 1 day trip and for this one one day was enough. Quite a long trip from Hanoi was rewarded by beautiful views of a Buddhist pagoda Chua Bai Dinh and mesmerizing nature afterwards.
The pagoda is the largest one in South East Asia and it was built in 2003. It offered not only praying spaces, but hundreds of different Buddha statues, a tower with an exceptional view and amazingly calm and relaxing spaces. Get ready to pay for a shuttle taking you there from the parking lot or for quite a long walk.
The nature is very similar to the one around Ha Long Bay, only it is not a bay but a river where you spend the whole time (except for a short walk on one island) on a tiny boat, so it is more personal. We saw beautiful flora on the majestic hills around and many caves through which we just went on the boat.
It was raining the whole time and even though I had a raincoat I ended up being all wet. Make sure to have something that will cover you even while sitting under the rain for hours on a wet chair and possibly another set of clothes for the way back - the air conditioned bus is not the best place to sit wet in.