I was able to achieve this very quickly by placing all the wonders on the map in the scenario editor.
- From the main menu, choose Tools -> Scenario Editor
- In the scenario editor, click Objects -> Place object...
- In the place objects window there is a black text box to filter objects; type WON to filter just the wonders (For me, there are 4 duplicates of every Wonder?)
- Simply place one of each of the wonders (excluding duplicates) and the achievement should unlock.
You can also click the 'Ignore placement restrictions' checkbox in the Objects menu to overlap wonders to save space if required.
If done right, this should unlock without even having to playtest the scenario.
This worked for me. I hope it works for you.