Players assume the role of a provincial governor to build thriving cities across the Roman Empire, in which they must ensure their citizens have their needs met, and deal with various disasters, angry gods and hostile enemies.

The developers of Caesar III designed the game in response to critiques of its predecessor, introducing branching missions, a merged map for city-building and combat, and a "walker" mechanic for citizens of the city to affect their surroundings.

[4] The Career mode of Caesar III follows a series of branching assignments requiring players to construct cities of increasing size and complexity.

Caesar III also features inhabitants that provide services to buildings by walking past them, adding an additional element of strategy to road pathing.

Favor ratings are measured by whether players fulfil in a timely manner the requests from Caesar to pay a tribute or provide gifts.

The editor allows players to produce their own scenarios from over twenty city locations, as well as choosing the identity of invaders, available buildings, and features on the map itself.

Simon Bradbury of Impressions Games stated the mechanic was introduced as "we wanted to do something different...we liked the SimCity sense (that) you place the building down and it affects things around it but we always found that was a bit static.

[10] The re-release removed the DRM requirement, fixed stability bugs with modern operating systems and has enabled players to continue to experience the game.

[17] In the German market, Caesar III had spent 10 weeks on Media Control's computer game sales charts by early 1999, with placements of sixth and ninth for the first and second halves of January, respectively.

[18] Late that year, the Verband der Unterhaltungssoftware Deutschland (VUD) gave Caesar III a "Gold" award for its commercial performance through September 1999,[19] indicating sales of at least 100,000 units across Germany, Austria and Switzerland.

[26] Similarly, Trent Ward of IGN remarked Caesar III was a "fantastic strategy game (that) is well thought, expertly designed, and artistically pleasing.

David Wildgoose of PC PowerPlay praised the game's "variety and immense subtlety of (its) economic and political models", creating "deep and highly addictive strategy".

[32] Eliot Fish of Hyper stated "Caesar III is far more complex and challenging than a straightforward city management sim".

[30] The interface design was also praised as intuitive, with Eliot Fish of Hyper observing "not only are the menus clear and informative, well structured and easy to access, but the graphics are brilliantly drawn and it's a cinch to visually keep track of what's going down.