Take a boat ride in Halong Bay
The famous world heritage site is well worth the hype. You can take day trips very easily from Hanoi. When there you can explore by canoeing or float around in bamboo raft. There are still communities that live out on the water and will likely be the person taking you to the water. The picture above was taken on a very cloudy day and so when they sky I clear you're in for an even bigger treat. Nearby there are also some impressive caves that will likely be included on your tour.
Lay on the beach in Nha Trang
A great spot in Vietnam to enjoy more of the beach bum resort side of the country. The beach here is a beautiful stretch of and doesn't get quite as crowded as a lot of beaches in Asia. Sit back and relax and there will always be someone nearby ready to hand you a beer.
Visit Hoa Lo Prison
A must visit in Hanoi. Hoa Lo Prison was originally used by French colonists and then later by North Vietnam for American Prisoners of War including US Politician John McCain. The museum takes you through what the prison was like under French rule in the early 1900's and then to how it was used during the Vietnam War.
Explore the Củ Chi tunnels
Best taken as a daytrip from Saigon, the Củ Chi tunnels are a network of tunnels that were used by the Viet Cong during the Vietnam war to assist there resistance against the Americans. They were used as hiding spots, to transport things and generally assist their operations. When you visit today, you will be taken around the preserved network, shown how they were used as well as Guerrilla warfare tactics. There is also part of the tunnels which you can walk through to see what it was like. Give it a go but it is a very tight squeeze.
Ho Chi Minh Museum
A great place to learn about Uncle Ho from his childhood into his political career up until the foundation of the Democratic Republic of Vietnam and his presidency. A good place to learn more about the country's recent history.
See the sand dunes of Mui Ne
Who doesn't love to slide down and dunes? Many tourist flock her to do just that. Mui Ne itself is also a nice coastal town with beach resorts and restaurants and bars.
Send a lantern down the canal in Hoi An
As previously mentioned, there are few places as picturesque as Hoi An. Here they host the Full Moon Lantern festival every month but you can pretty much buy lanterns at any time. At dusk purchase a few of these and watch them sail along the river through this atmospheric little town.