Hi there,

I've got a few days spare in Hanoi and I'd like to check out the day trip options from here. I know very little about the destinations so any advice on day trips and companies that run them would be perfect. Thanks.

Halong Bay (Overnight on junk/ Cat Ba island) and Ninh Binh (Overnight in Tam Coc) - A day trip is not highly advised.

We took a day trip to the Perfume Pagoda.

But Hanoi itself has so much to offer, don't be too quick to go out of town.

Difficult to recommend anything without knowing what sort of interests you have? Hanoi is a huge sprawling city so it takes along time to get out of town in any direction making day trips outside the city difficult. As Kathie says, there is a lot to see in the city itself and just to see the main sites a enjoy some of what the city as to offer will likely take up 3-4 days.
Duong Lam ancient village is possible in a day and you could visit a few of the craft villages in the suburbs in a day.

Ninh Binh, mai Chau and Ha Long really do need an overnight stay AND you need to be careful where you visit in those places to avoid massive crowds, especially at weekends.

While you are in Hanoi I would recommend the Thang Long Water Puppet Theater.