I'm writing a grid-based 2D game in Unity3D that would ideally use grid sizes of around 200x200 or so, with multiple zoom levels, including all the way out. When I tried render a 200x200 grid at the most zoomed-out level where everything is visible, Unity crapped out saying that there were too many vertices to attempt to draw. This makes sense, as it's trying to render 40,000 sprites.
I was wondering, how do games like Dwarf Fortress and OpenTTD manage so many sprites at once on the screen when the map is zoomed out all the way? Are there any general strategies for handling the rendering of a large number of sprites such as this?