To improve security and illegal immigration, the European Union (consisting of 26 countries) has voted to require travelers from Visa-free nations (such as the U.S.) to register their travel before entering the country beginning in 2021. Technically not a Visa, it functions as one, but can be easily obtained online for a small fee.  Once approved (usually instantly), access is granted for 3 years.  Watch for more information as this date draws near.