Obama and Russian President Dmitry Medvedev will sign the nuclear arms reduction treaty at a ceremony in Prague. From the White House:
On Wednesday evening, the President will travel to Prague, arriving Thursday morning local time. The President will attend a bilateral meeting with President Medvedev of Russia, followed by a signing ceremony and a press conference with Presidents Obama and Medvedev. The President will then attend a ceremonial lunch with the three countries - the United States, Russia and the Czech Republic. On Thursday night, the President will attend a dinner with 11 heads of state and government from Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia, and Slovenia.
On Friday morning, the President will attend a bilateral meeting with the President and the Prime Minister of the Czech Republic, before returning to Washington and landing that night.