Cut out the two pieces of the hotel building in the upper left of the postcard.

Note that one of the folds on the front of the hotel is a reverse fold (score on the back). Fold the walls of the hotel to match the exact shape of the roof. Glue the walls together and then glue the roof flat.

Cut out the smaller elevator section of the hotel. Use a tweezer to help fold the small tabs. Assemble into a rectangular box. Glue the elevator section to the roof and back of the hotel.

Cut out the shorter office building. Note that two of the folds on the office building are reverse folds (score on the back). Fold the walls to match the exact shape of the roof. Glue the walls to the tabs on the roof.

Cut out the IDS tower. Score and fold into an octagonal shape to match the roof. Glue the walls together and glue the roof in place.

Score and cut out the base of the IDS Center. Glue the walls of the base square. Note the small reverse fold for the walls near the base of the tower.

Glue the tower to the base, with the tabs on the tower matched up to the place indicated on the base. The octagonal end of the base fits into the bottom of the tower.

Glue the hotel building to the top and side of the base in front of the Crystal Court.

If you are interested in adding more detail, you can cut out the tiny rooftop building for the window washing equipment and add this to the top of the tower.