fantastic is an adjective, meaning of an extraordinary or improbable nature, sometimes connoting extreme favor or approval. It is used to describe people, places, or things. It is often used in an exclamatory sense, to emphasize the positive qualities of something.
when used as an adjective, fantastic usually precedes the word it is modifying. It should not be used to describe concrete objects, rather something abstract.
The food at that restaurant was fantastic.
My friend just got a fantastic new job.
The singer's performance was absolutely fantastic.
remember not to use fantastic to describe concrete objects, rather than something abstract.