Step 1:
Prefold in half over this line.

Step 6:
Make a valley-fold over these 2 lines (they are a bit curved). The ends at the 2 arrows are pulled upwards a little when you make these folds.

Step 5:
Fold the piece above the black line downwards by making a valley-fold over this black line.

Step 2:
Make an inside reverse fold over these 3 lines.

Step 4:
Fold the model in half over these prefolded lines.

Step 3:
Make another inside reverse fold on the edge you've made in step 2.

Step 10:
Turn the model.

Step 8:
Make a valley-fold over the line at the left and a mountain-fold over the line at the right. Make these folds over all paper layers in once.

Step 9:
Make a mountain-fold over the line at the left and a valley-fold over the line at the right. Make these folds over all paper layers too.

Step 7:
And make a valley-fold over these 2 (curved) lines.

Step 16:
Prefold the model over these lines.

Step 15:
This note is for the base of the eiffel tower. Fold the paper in half over this line

Step 12:
Make a mountain-fold over this line. Pull the flap (see arrows) upwards.

Step 11:
Make a valley-fold over this line.

Step 14:
One piece of the tower is done now... Make one more exactly like this one (step 1-13).

Step 13:
The 2 arrows show the flap of step 12

Step 21:
Hold the 2 edges indicated by the large arrows on their place with one hand. Then, push the flap indicated by the small arrow flat with your other hand. Do this by making a mountain-fold over the 3 lines in the middle and a valley-fold over the 2 outer lines.

Step 19:
Fold the edge below and the edge at the right downwards by making a mountain-fold over the 2 (prefolded) red lines. Pull the corner at the bottom-right outwards while you are making these folds (=mountain-fold over the black line in the middle and a valley-fold over the 2 outer black lines).

Step 20:
Repeat step 19 at the other 3 corners, see arrows.

Step 18:
And prefold over these 4 lines.

Step 17:
Prefold over these 4 lines.

Step 22:
Repeat step 21 on the other 3 flaps, see arrows.

Step 28:
Place the top of the tower on the base.

Step 25:
Slide the edge indicated by the yellow arrow below under the edge at the upper yellow arrow. (Slide in the direction of the orange arrows). Now the 2 pieces are connected.

Step 26:
Push the tip indicated by the small orange arrow to the corner at the large orange arrow. And push the tip indicated by the small yellow arrow to the corner at the large yellow arrow. Then, push the top of the tower flat from aside, see red arrows.

Step 24:
And the base of the eiffel tower is ready too...

Step 23:
Fold the edge indicated by the arrow below to the inside of the model by making a mountain-fold over the black line. Make the same fold on the other 3 edges, see upper arrows.

Step 27:
Press the top of the tower a little further flat, see arrows. Then, make a mountain-fold over the short black line. (Make this fold over all paper layers).