I’ve come across a few websites that make it easy to generate 3D models from terrain. The best part is that you can get relatively high quality models from these sites for free.
CADMapper is fantastic for creating detailed models, down to the level of individual buildings, and is free for areas up to 1 square kilometer. The site also has whole-city models for over 200 cities worldwide. Want to print Paris? Buy a spool of filament and go for it!
For terrain models of much larger areas, I’ve tried all kinds of methods, including downloading GIS data from USGS and using software utilities to create .stl models. But none of these work as well for me as Terrain2STL. The model of San Diego county in Southern California was generated from this site.
A final site I’m aware of is Terrain Party. It’s less intuitive to use than the other sites, but is also free and can produce good results.
If anyone’s familiar with other utility sites for 3D printing, please let me know via comments.