We went to Lotte Observation Deck, and we enjoyed the view of Hanoi from the top. You can spend around 2 - 3 hours, and they have Lotte burger, some other cafes.

We had heard about this place so got a taxi to here...great view of Hanoi...get your photo taken on the glass floor by a professional photographer...scary if you don't like hights.

Grateful & Thankful To have the opportunity to experience the Lotte Observation Deck in Hanoi. Situated on the 65th floor, 253 meter, 830ft high. Amazed and mesmerized by the design and architecture of the tower deck with its 3D design lift that brought us up...More

Great views from the top and a decent way to spend some time in Hanoi which has very few activities otherwise. Don’t bother with the shopping centre unless you’ve got a fair bit of cash to spend.

Go to the top of the hotel (roof lounge) and save the cost of the observation deck. You will find yourself on the roof with stunning views (great at night) and a bar that serves good food and drinks, if pricey by Ha Noi standards....More

I mean you should go there, definitely by night to see the nightlife of hanoi through the see through glass here but the entrance ticket is not that affordable.

You can really get a sense of the city from the observation deck. It is bigger and more spread out than I thought.