Getting in to Belarus was complicated by their visa rules. If a US passport holder is going to stay more than 30 days you have to have a visa and these are time consuming to get and costly too.
If a US passport holder is going to stay less than 30 days you can fly into the International Airport in Minsk and not have to get a visa. If you are coming in any other way then you do need a visa.
So to avoid the visa acquisition process I took a 25 minute flight from Vilnius to Minsk. It was less expense than getting a visa and cut out having to send my passport to yet another embassy as I had to do to visit St Petersburg.
Also as a side note, for a US passport holder to travel directly between Belarus and Russia you must have visas for both Belarus and Russia and you must arrive and depart from Minsk International Airport.