Uh!, John. I said brief!
However, I can see you've put a lot of work into this so here you are.

Materials.

Item 1. Empty plastic Tesco salad dressing bottle. Eiffel Tower shape. 17cm tall x 5cm at base.

Item 2. Empty Aldi Caramel Mousse pot. Trumpet shape. 9.5cm tall x 5cm at base. Mouth 9.cm.

Item 3. Three empty plastic fruit and jelly containers. Bowl shaped. 5cm tall x 8cm at mouth. 3.5 at base.

Item 4. White plastic Asti bottle stopper.

Item 5. Expanded polystyrene packing c. 2 to 3cm thick.

Item 6. One white plastic cable tie. (Any colour will do).

Item 7. Cork for talon finials of tower. Cannibalise from wine corks.

Item 8. Some fine sand.

Item 9. 'bond it' high viscosity superglue.

Item 10. White PVA wood glue.

Item 11. One lolly stick.

Item 12. Couple of dozen small rocks from the garden. Approx. size 3cm x 2cm.

Item 13. Small piece of 3 ply. .5 of a mm thick. 10cm x 10cm square.

Item 14. Tetrion white filler powder.

Item 15. Range of acrylic paints.

Item 16. Various small paint brushes.

Item 17. A piece of kitchen tin foil.

Method:

Glue item 1 to the base of  item 2 with item 9.

Fill item 1 with item 8.

Glue item 3 one inside the other with item 9.

Fill item 2 with mixed filler.

While still wet press glued item 3 inside the flared end of  item 2. Excess filler will squeeze out. Remove excess and smooth round with a damp finger. Make sure the final visible rim of  item 3 is clean of filler.

Cut four strips of  item 5 to c. 4cm wide x  22cm long. Shape them roughly to a 'D' profile.

Glue all four equidistant from base to top around your finished plastic core with item 9. (Take care as the action of the adhesive on the plastic surfaces will generate heat effectively welding item 5 to the bottle etc.). They should join at the top.

Glue the screwtop of item 1 permanently in place with a small amount of item 9.

Glue item 4 to the screwtop of item 1 with the fins facing up.

Mix item 14 with a small amount of fine sand, a couple of teaspoons of  item 10 and mix to a plaster consistency with water.

Begin moulding tower over item 5 into four fused half-round towers which will meet at the top.

Press suitable sized piece of item 11 into wet mortar where the door will be.

Leave a space at the top of the towers to make the talon finials,

While your mortar is wet, press item 17, crumpled kitchen tin foil, into the surface to create fissures and the appearance of undressed rock.

Cut four talon finials from cork. Cut slot to fit over fins of item 4. Glue in place with item 9.

When secure continue moulding to the top of the finials which should also be covered and shaped with your mortar.

Glue or press in  to wet mortar suitable stones, item 12, in natural pattern. It is possible to mould rock outcrops from your moulding mortar mix. My model uses both techniques.

Glue item 13 to base with item 9.

Paint and dry brush to achieve the look of rock. Seal the finish if you wish.

If you want a surrounding diorama then dress a piece of ply with fallen rocks, scree and gravel.

Glue your tower to this.

I think that covers it.