Hatirjheel is a large lake and road-and-bridge system in central Dhaka, built around water that once sat neglected in the middle of the city. It is not old Dhaka, but it is one of the clearest places to see the city's modern scale and appetite for infrastructure.
The best reason to come is for an evening walk or drive, when the bridges and flyovers are lit and the water gives the city some rare open space.