In Russian folklore Rostov is "Father" a criminal capital of early soviet times. Not so criminal now, but there are some districts with private houses just one block from the center to river where people prefer not walk in dark time. I doubt you will find something interesting to see in Rostov. Rostov governors made good job to make the city look ugly. May be some restaurants on the left side of Don river and a farm market in the center.
O haven't been but as provincial Russian cuties I imagine it is fairly well up there.
Which app would be better?