Hi in this instructable I will show you how to make secret location for your small things that looks like a rock
Enjoy.

Step 1: Supplies

You will need:
-pair of plastic gloves
-water
-scale
-water baloon
-gypsum( depending on the type of it you have more or less time before it harden)
-tissues
-empty can
-black paint
-brush
If you have a dremel and baloon pump it will make your work easier.

Step 2: Baloon

Blow the baloon . I had to use a pump but you might be able to do it without one.

Step 3: Making Gypsum

Using scale measure quantity of ingreadiences
Use proportions from gypsum bag
For my baloon I used about 250 g of already made gypsum

Step 4:

Dip tissues in gypsum and place them on the baloon repeatedly until you run out of gypsum (if you feel like you need to make them really thick). If no, use as many as it is needed to make the walls solid

Step 5: Drying

Leave gypsum for 24 hours to dry or put it in oven but BE CAREFUL, pop the baloon before putting in the oven or gypsum can fall apart as the air in balon expends.

Step 6: Removing Baloon

Cut a hole in rock and remove the baloon (I used dremel but you can do this in other way)
Remove baloon from rock

Step 7: Painting

Paint rock using black paint
You can dip brush in water to get paint to every place

Step 8: End Result

Wait untill paint dries and it's ready !
You can hide anything in this rock : spare keys, money or any documents.
Place it nearby a real rock for a better effect.
Hope you enjoyed this guide !
If you have any questions send me message, I will try my best answering it.