Chancellor Angela Merkel rolled out the red carpet for US President Barack Obama when he arrived in Germany on Friday for NATO's 60th anniversary summit, dpa reported.
The president flew in by helicopter from the French city of Strasbourg, joint host of the two-day gathering with Baden-Baden, a spa town in the western foothills of the Black Forest.
Obama inspected an honour guard of the German armed forces after a military band played the German and US national anthems in the town's cobblestone main square.
Merkel and Obama then strolled across the square, stopping to chat and shake hands with well-wishers on a cloudless spring day.
The two leaders, accompanied by their respective spouses, then entered the historic town hall where the president signed the visitors book before holding political talks with the chancellor.
Strict security measures were in force for the visit, Obama's first to Germany since his inauguration as president in January.
Some 14,600 police were guarding Obama and the other 27 heads of state and government attending the summit functions in Baden-Baden and Kehl on the German side of the Rhine river.
German security officials were bracing for up to 25,000 anti-NATO campaigners to turn up, around 3,000 of whom have been classified as militant.
Police said 500 protesters took part in an anti-NATO rally on Friday afternoon. The peaceful protest was held on the outskirts of Baden-Baden after a court banned demonstrations in the city centre.
Police set up security zones were set up around key venues in the town, including the hotel where Merkel is staying and the building where the leaders held their opening dinner on Friday evening.
Protesters have registered 13 separate demonstrations in the two summit locations in Germany. They have also threatened to block roads and carry out other acts of civil disobedience.
Germany is providing 600 soldiers to help protect the summit, while NATO will deploy AWACS surveillance aircraft. Shipping along the Rhine will be halted on Saturday morning when the heads of state and government pose for photographs on a bridge linking Strasbourg to the German side.