"The game is divided in 3 parts, named after the three traditional eras of Ancient Rome: Kingdom, Republic and Empire.
In a departure from older versions in the series, Caesar IV is equipped with variable, realistic 3D instead of fixed, isometric 3D. This means more realistic landscapes and city views, and the ability for players to better see and use game building space. In addition, buildings and roads may be placed at 45 degree angles to the playing grid, as well as aligned with the grid, allowing game players more options in creating efficient and visually appealing city layouts.
Source: Wikipedia, "Caesar_IV," available under the CC-BY-SA License.