Praise be to Allaah.

Many texts indicate that Paradise and Hell are two creations which currently exist, and that the Prophet (peace and blessings of Allaah be upon him) saw Paradise and Hell. This is proven by many events, for example: 

The hadeeth of ‘Abd-Allaah ibn ‘Abbaas, who said: “There was an eclipse of the sun during the time of the Messenger of Allaah (peace and blessings of Allaah be upon him), and the Messenger of Allaah (peace and blessings of Allaah be upon him) prayed… Then he said, ‘The sun and the moon are two of the signs of Allah. They do not become eclipsed because of the death of somebody or because of his life (i.e. birth). So when you see them, remember Allaah.’ The people said, O Messenger of Allaah, we saw you taking something from where you were standing, and then we saw you retreating.’ The Prophet (peace and blessings of Allaah be upon him) replied, ‘I saw Paradise and stretched my hands towards a bunch (of its fruits) and had I taken it, you would have eaten from it as long as the world remains. I also saw the Hell-fire and I had never seen such a horrible sight. I saw that most of its inhabitants were women.’ The people asked, ‘O Messenger of Allaah, why is that?’ The Prophet (peace and blessings of Allaah be upon him) replied, ‘Because of their ungratefulness.’ It was asked, ‘Are they ungrateful to Allaah?’ The Prophet (peace and blessings of Allaah be upon him) said, ‘They are ungrateful to their life companions (husbands) and ungrateful for good deeds. If you are kind towards one of them throughout life, then she sees anything (undesirable) in you, she will say, “I have never seen anything good from you.”’”

(This version narrated by al-Bukhaari, 1052; also narrated by Muslim, 901) 

And the Prophet (peace and blessings of Allaah be upon him) saw Paradise in his dreams, and the dreams of the Prophets are a form of wahy (revelation) and are true; he saw al-Rumaysa’ in Paradise; he saw a palace belonging to ‘Umar ibn al-Khattaab in Paradise; and he saw Paradise on the night of the Mi’raaj when the Sidrah (lote-tree of the utmost boundary) was covered with what it was covered with. And Allaah knows best.