Like literally anything interesting that could be included as a landmark? I'm not really familiar with the genre. Also, what level of civilization?
I would figure out some representative civilizations for your areas (jungle and tundra or however you frame it) and look at the wikipedia articles, then make go through their respective galleries on wikimedia commons (which are generally linked from the main article in a little box near the end of the wikipedia articles). So for example look at Maya then look at the Category:Maya on wikimedia commons, which should give you some unique looking stuff like this: http://upload.wikimedia.org/wikipedia/commons/5/5f/Plaza_of_the_Seven_Temples_-_Structure_5D-94.jpg.
Other randoms things:
- Well (water source)
- Swimming hole
- Big Old Sacred Tree of Holiness or Whatever
- Sacred sites
- Jungle clearing (meadow)
- Tree house