Just in case anybody else was wondering, downtown Austin is mostly obscured due to local elevation changes rather than curvature of the earth.
Downtown is about 14 miles away from 183/45. Assuming the surrounding area was completely flat (and didn't have hills), this would result in a downward curvature of about 136 feet. This would hide the first 10-12 floors of downtown buildings.
Ok, but hold on, we are on top of a flyover, which I will approximate is about 100 feet tall. The true horizon from the flyover (again, assuming flat ground) is about 12 miles which would let us see most of the CBD. Therefore, curvature of the earth is not the culprit.
Now, looking at local elevation effects: CBD is at about 500 ft above sea level. The 45/183 interchange is at about 930 ft. If we make some gross geometric assumptions, this difference of 430 feet (131m) would obscure all buildings except for the Frost, Austonian, The W, 360, and Spring. (
Source)
As it turns out, you can see those buildings along the horizon, in left to right horizon order, if you look carefully at the first and second images above. The W and Spring rooftops are not easily recognizable since they are shorter and don't have barely distinguishable roof features. When it is done, the Fairmont spire will be visible, but probably hard to make out. The Independence will presumably fill in the gulf between the 360 and Spring.
In conclusion: Austin needs taller buildings.
