The visit of Jurjan is one of the miracles of Imam Al-Hassan Al-'Askari (peace be upon him)..

The Infallible Imams (peace be upon them) have a special attachment to God and the unseen because of their status of infallibility and Imamate, and they have miracles that prove this attachment. And among the miracles of Imam Al-Hassan Al-'Askari (peace be upon him) is what happened the third of Rabi' Ath-Thani he traveled miraculously from Samarra to the Iranian city of "Jurjan" located between "Shahrood" and "Bandar Shah" and overlooks on the Caspian Sea.
Jaffar Jurjani: says, "I went for Hajj and visited Imam Al'Askari (peace be upon him) I had the money for Imam (peace be upon him), which his friends had sent to him. I wanted to ask the Imam (peace be upon him) to whom I might surrender that. When I visited him before my saying something he said, Handover the money, which you have with you, to my servant "Mubarrak".
I handed the money over to him and told Imam (peace be upon him) that his friends in Jurjan conveyed their regards and salutation to him. He said, "Aren't you returning after the completion of the Hajj." I said: Yes. He (peace be upon him) said: After 170 days you will reach your hometown on Friday, 3rd Rabi' Ath-Thani, in the beginning of the day, inform them that I will visit them at the end of the afternoon of that day. And do back wisely and the Almighty will protect you and those with you, so be at the front of your family and children. God will give you a son. Name him As-Salt Ibn Sharif.Ibn Ja'far Ibn Sharif. He will become one of our followers.
Then I said: O son of the Messenger of Allah, Ibrahim Ibn Isma'il Jurjani is one of your Shia and he does lot of good to your followers, every year he donates of his wealth more than hundred thousand dirhams, and he is one of the wealthy people of Jurjan. The Imam (peace be upon him) said: May God reward Abi Is'haq Ibrahim Ibn Isma'il for his deeds towards our Shia, may his sins be forgiven and his reward a healthy boy who says the truth, tell him: Al-Hassan Ibn Ali tells you, name your son Ahmad.
I proceeded to Mecca and returned safely to Jurjan exactly on the same day the Imam had foretold. In the beginning of the Friday third of Rabi' Ath-Thani. My friends came to congratulate me and I promised them that the Imam has promised that he will come to visit at the end of the afternoon, so you would have an opportunity to address all you questions to the Imam (peace be upon him).
After praying Dohr and 'Asr, they gathered all in my house. And I swear by Allah that Abu Mohammad came to us, and greeted us first, so we welcomed him and kissed his hand. Then he said: I had promised Ja'far Ibn Sharif to visit you at the end of this day. So, I prayed Dohr and 'Asr at "Surra man Ra'a [Samarra]" and came to you to renew the covenant, and here I am with you now, you can ask all your questions.
The first who began was Nadhr Ibn Jabir, who has requested the Imam to pray for restoration of eyesight of his son, he passed his hands over his eyes and cured his blindness, then returned the same day."