1. Select your UNESCO site;
2. Make a precise digital drawing of the part (a building, a statue etc.) that you want to make accessible;
3. Put it in a 3D printer;
4. Get a resin model and wash it with alcohol.
Did it ? What we have now is just the positive mould of our object. So:
5. Pour the silicon into the positive mould.
6. It is time to cast: now we can fill the negative mould with jesmonite (a gypsum-based material).