The highway that runs from the airport to the centre of Beirut has been decorated with Iranian flags and posters welcoming President Mahmoud Ahmadinejad. So have the roads that go south, which he will take when he visits villages on the Israeli border.
Mr Ahmadinejad has been invited by the Lebanese head of state, Michel Suleiman. But his meetings with the head of Hezbollah, his fellow Shia Hassan Nasrallah, will be more important.
Hezbollah is a Shia Muslim religious, political and social movement, as well as Lebanon's most powerful armed group and an implacable enemy of Israel. What has made them that, above all, is their hostility to Israel.
Mr Ahmadinejad will be a welcome guest in Shia areas of Lebanon. Iran paid for much of the reconstruction that was necessary after the war with Israel in 2006. The money, starting out with a bundle of US dollars for everyone whose house had been destroyed, was channeled through Hezbollah.
But as ever in Lebanon, where power is split between the religious communities, one person's hero is another's nightmare. Samir Geagea, the leader of the Christian Lebanese Forces party, and a strong opponent of Hezbollah, said that Mr Ahmadinejad would be welcome if he behaved like the president of Iran, but not "if he behaves like president of part of Lebanon".
Visits of foreign dignitaries can be an unpleasant reminder of Lebanon's place in the Middle East.
The problem is not that the offers of help and support they bring with them have strings attached. That is the way international politics works. It is more that big and powerful guests can make some Lebanese feel that they are pawns in a game they cannot control, or even influence all that much.
Sectarian and political tensions rose steadily throughout the summer in Beirut.
The reason this time is the UN's special tribunal for Lebanon, which was set up in 2005 to investigate the assassination of former Prime Minister Rafik Hariri and the wave of political killings that followed. The tribunal is believed to be close to issuing indictments, including ones naming members of Hezbollah.
The current Lebanese prime minister is Rafik Hariri's son, Saad. He is under unrelenting pressure from Hezbollah and Syria to denounce the tribunal that was set up to investigate his father's assassination, BBC reported.
