Walk through cobbled streets,
And past Frank Zappa's statue,
To a delicious meal.
The haiku above is an example of how you can spend some time in Vilnius, if you want to do it as I did. I visited in 2014, and I think I was expecting Lithuania to be a bit more ex-Soviet and a bit less Western European than it actually is.
One can spend quite a while just walking through the streets, taking in the sights, shopping, and sightseeing, and then take a well-earned rest at the end of the day. I had one fabulous dinner that was a highlight, too. I would definitely recommend Vilnius as a chilled and different location for a weekend visit for someone from the UK, for example.