A descriptive compostion about a place or building should consist of:
A) An intoduction in which you identify it, give its exact location and state the reason for choosing it.
B) A main body in which you describe the main aspects of the place or building in detail.
C) A conclusion in which you mention your feelings and your final thoughts about the place or give a recommendation.
* Introduction
Paragraph 1: set the scene (name and location of the place/building, reason for choosing the place/building).
* Main Body
Paragraph 2, 3: overall look and particular deatails (place: sights, facilities, free-time activities building: first look and specific details).
* Conclusion
Feelings and final thoughts about the place/building and/or a recommendation.
- This link gives you a better explanation about how you should write your composition.
http://www.slideshare.net/aponce4/writing-describing-places#btnNext
