Download GO Map 3D Map for AR Gaming FREE Unity. 

It is a dynamic map SDK for making location-based games with unity 3D.
Highly customizable with the classic Unity inspector interface GO Map is the easiest map plugin around.
Choose among various examples to fully understand GO Map capabilities and build every demo scene on your smartphone using real GPS position in few clicks

It now includes GO Terrain! Enjoy maps with elevation, satellite images and lots of more features! …

Official Website
Documentation
Unity Forum
Web Demo