The place must have a name that has a funny or lewd meaning in English. The spelling of the name needs to be similar to the matching English word, or sound similar when pronounced the way an English speaker would pronouce it.
The place must be a town, or another type of place that does not get renamed under normal circumstances, such as a street name, bridge, mountain, or national park. If the place is not a town, it will be marked yellow on the map.
The place must have some type of sign displaying its name.
The place and its sign must be accessible by reasonable means of transportation, such as driving or a short hike.