The 2 km long mural is worth a walk if you have some spare time in Hanoi. It's especially interesting to see after you have visited some national landmarks as it shows the history and landmarks of Vietnamese people. It commemorates the 1000 years of the founding of Hanoi.
It's hard to take pictures of it though as the sidewalk is quite narrow and the traffic on the road is busy, so be careful when visiting this place.
Wikipedia https://en.wikipedia.org/wiki/Hanoi_Ceramic_Mosaic_Mural
Address 40 Phố Yên Phu, Trúc Bạch, Vietnam
Coordinates 21°2'48.611" N 105°50'38.175" E