Vilnius Old Town is compact. You can walk end to end in fifteen minutes, past baroque churches and Soviet yard doors and the occasional cat. The drinking options are not compact. There are too many, and most of them are fine. Here is how to think about where to go.
The main streets
Pilies gatvė and Vokiečių gatvė carry the tourist current. The bars here are loud, lit up, often good enough. They serve beer and basic cocktails at prices that make sense for a capital city that is still, somehow, affordable. If you are visiting Vilnius for the first time, you will end up here. That is fine. Drink your beer, watch the street, move on when the music gets too much.
The side streets
The more interesting bars in Vilnius Old Town tend to be a turn or two off the main drag. Stiklių gatvė -- the old glassmakers' street -- runs parallel to Pilies, quieter and narrower. This is where you go when you want to sit, not stand. When you want a proper cocktail, not a pitcher. A few of the best cocktail bars in Vilnius have set up on these side streets, where the rent is lower and the crowd is different.
What to look for
The cocktail scene in Vilnius has grown. A few years ago, your options were mojitos and Long Islands. Now there are bars making proper drinks -- balanced, seasonal, sometimes with local ingredients. Look for places that keep the menu short. A bar with ten cocktails and all of them good is better than a bar with fifty and a laminated menu.
Price is a useful signal. In Vilnius Old Town, a well-made cocktail runs around nine to ten euros. That is roughly half of what you would pay in London or Paris for the same drink. Wine by the glass starts around six. If a place is charging significantly less, the liquor is probably not what you want it to be.
A place on Stiklių
Vanagai is at Stiklių g. 4, a few doors from the corner. The name means hawks -- a reference that Lithuanians will understand and visitors can look up. The walls are dark green, the light is low, and the cocktails lean botanical: forest berries, cherry, pine, things that grow in this country and make sense in a glass.
The signature cocktails are ten euros. There are seven kinds of spritz at nine euros each if you want something lighter. Wine starts at six. The hours run late -- until two on weeknights, three on Fridays and Saturdays. Closed Mondays.
It is not trying to be the loudest place on the street. If you want where to drink in Vilnius Old Town and actually hear the person you came with, walk down Stiklių.
The practical part
Most bars in Vilnius Old Town open around five or six in the evening. Kitchen service, where it exists, tends to stop before midnight. Cards are accepted everywhere. Tips are not expected but appreciated. And the walk home through Old Town at two in the morning, past the cathedral and the river, is one of the better parts of the evening.