Chișinău isn't a pretty capital and doesn't pretend to be. It was first mentioned in 1436 as a monastery village, got a tidy grid of streets after Russia took Bessarabia in 1812, was damaged by the earthquake of 10 November 1940 and then by the war, and was rebuilt in the Soviet years. What you see is that last layer: wide boulevards, concrete blocks, a few survivors of the 19th century and a lot of trees.
It is a small, cheap city that works best as a base for wine. The center takes a day, the Soviet landmarks half of another, and the rest goes to the cellars and the cliffs of Orheiul Vechi, which are why most people come. Three days is the right length because the city is compact and the sights outside it are within about an hour's drive.
Day one is the center on foot: the park, the arch, the cathedral and the central market. Day two is the National Museum of History, the Soviet towers and an afternoon tour of Mileștii Mici. Day three is the day trip north to Cricova and Orheiul Vechi. Start on a Tuesday: the history museum is closed on Mondays, and the cellars need booking ahead, so arrange them before you land. More on the country is on our Moldova page, and if you're coming from Romania, 5 Days in Bucharest is the natural first half of the trip.