Your humble host's seasonal gift to you devoted readers is a custom level of the Warden for your Metamorphosis Alpha edification. This level features full scale replicas of 'wonders of the world' and other structures of historical and cultural import. As long as there's the space to do it, why not have recreations of these structures so that the colonists can have a better appreciation of their human heritage? This is the layout before the disaster; feel free to add radiation zones and whatever details you see fit. You can have type-4 humanoids inhabiting Petra and Angkor Wat infested by sword bushes!
The approximate scale of each hex is: 3 miles (4.83 km) from side to opposite side or 3.464 miles (5.577 km) from corner to opposite corner. Depending on which level this represents, the scale will vary slightly, but unless the characters have surveyor's tools (and know how to use them) they're not going to notice the meager difference. Please note, since there is no curvature of the Earth, there is no horizon per se.
On the map, the thick gray line represents a simulated section of the Great Wall of China. For other features, please refer to the following key: