While the capital effortlessly attracts foreigners, one factor often prevents them from staying for long: its pollution.
The suffocating air in the city is particularly bad in the winter as cooler air sinks to the ground. The high density of this cooler air acts as a blanket and traps pollutants, leaving them unable to disperse the way they do in the summer and essentially with nowhere to go.
The effect of this smog is evident. The World Health Organization (WHO) found that more than 60,000 deaths from heart disease, stroke, lung cancer, chronic obstructive pulmonary disease and pneumonia in Vietnam in 2016 were linked to air pollution.
Tom Traxson, who previously lived in Hanoi, made the decision to leave the city in the last two years when his Vietnamese wife gave birth to their son.
Traxson recalls how the situation left him with no choice: "It was the biggest factor in us moving, because my son had some respiratory problems. It was not directly connected to the pollution, but I'm sure that didn't help at all."
Many expatriates based in Hanoi are infatuated with the city, but feel helpless with the situation and how little it seems to be improving.
"In Hanoi it goes above 200 quite regularly, but in Saigon in the wet season it's normally pretty good. It was the number one factor in moving. Although I love Hanoi, it was a big reason due to the little one being born."
When the index value for air quality is above 200, it is recommended that children, active adults, and people with respiratory disease, such as asthma, should avoid outdoor exertions.
Not exactly ideal for any family that has children.
Another foreigner who, after spending five years in Hanoi, left the northern city recently is Matt Blacker. He also felt the situation had become untenable after noticing how rarely the AQI dipped below 150 for months at a time.
He says: "The air pollution definitely began to affect my quality of life after a while in the city. During periods when the air quality was over 200 or sometimes even 300 I'd spend days at home, with two air purifiers running day and night.
"I'd only leave the house if I had to go to work - wearing a half-face respirator mask that people use for painting or construction. I realized I couldn't take advantage of all the things to do in Hanoi without the ever present reminder that I was breathing poisonous air whenever I was outside."
He also compares the situation in Hanoi with Ho Chi Minh City, where he currently resides: "While the pollution here is pretty terrible as well, I can confidently say it's nowhere near as bad as Hanoi. During the dry season the AQI gets up to above 150 in the mornings, but usually gets down to under 100 by the end of the day. During the rainy season it usually hovers around the 50-100 mark most of the time. I still wear a mask and run air purifiers at home, but the pollution feels much less oppressive than it does in Hanoi."
For many, the mood is bleak since, as Hanoi continues to industrialize and urbanize at a rapid rate, the situation could worsen before getting better.
Traxson says: "It’s hard to say how to improve it without knowing the biggest contributor. Obviously everyone is aware of the burning of trash, which you see less of in Saigon."
Data from Hanoi's Department of Environment and Natural Resources in late 2019 showed that the city emitted 1,870 tons of carbon dioxide from burning 528 tons of charcoal every day.
People also burn grass and stubble leftover from the harvest to prepare the ground for the next crop.
"Hundreds and thousands of hectares of land surrounding Hanoi are incinerated," air quality evaluation site IQ Air said.