Everything that can be said about Kernave has already been mentioned on this site - it is a reasonably interesting site that makes for a nice excursion from Vilnius and has a modern, well-presented museum next to it. You can easily imagine the forts on top of the huge mounds and the location of the village by the river below. I'm glad I went there as part of our guided trip, as it seems a bit difficult to reach by public transport.