1998 · Rome

Caesar III

Setting
Roman Empire
Developer
Impressions Games
Publisher
Sierra Studios

The archetype. Isometric 2D sprites on .sg2 + .555 assets, .map scenarios, .sav saves. The official map editor landed in the v1.1 patch — the engine every later title in this era shares.

Caesar III screenshot
Community screenshot — Caesar III (1998) © Activision

Credits

Designer
David Lester
Programming
Simon Bradbury
Producer
Eric Ouellette
Art Director (US)
Darrin Horbal
Artists (US)
Ron Alpert, Adam Carriuolo, Bob Curtis, Mike Malone, Heidi Mann, Andrea Muzeroll, Dennis Rose
Artists (UK)
Gary Bendilow, Michael Best, Martin Povey, Daniel Shutt
Map & Assignment Designers
Doug Gonya, Eric Ouellette, Ken Parker, Greg Sheppard
Manual & Research
David Lester, Ken Parker, Wayne McCaul
Music
Rob Euvino
Sound Effects
Edward Saltzman
QA Manager
Jon Payne
Lead Tester
Greg Sheppard
Quality Assurance (US)
Brian Coons, Frank Lavoie, Tony Leier, Wayne McCaul, Tom Rogers
Quality Assurance (UK)
Neal Sumsion, Niall Callaghan, Austin Parsons
Special Thanks
Chris Beatrice, Doug Gonya

Transcribed from the Caesar III manual (Impressions Games / Sierra) ↗.

File formats

.sg2 / .sg3 + .555 → Documented. An .sg2/.sg3 index over pixel data held in sibling .555 files — the shared art pipeline for the whole isometric era.
Documented
.eng → Documented. Holds every string in the game, plus the layout of the message dialogs — the file any translation has to go through.
Documented
.map → Structure confirmed: ten uncompressed chunks in a fixed order, 211,692 bytes exactly. The scenario block's own internals are not documented.
Partially documented
.sav → Container structure confirmed from Julius: an ordered chunk list, most chunks compressed with PKWARE DCL. What is inside most chunks is not documented.
Partially documented
c3_model.txt → Documented. The plain-text file holding every building's cost and labour requirement — the one modders edit to rebalance the game.
Documented

Buildings

100 buildings → Every building the engine defines, with its footprint in tiles and the constant that names it in the source. Filterable by name or category.

Housing

20 rungs -> The ladder a citizen climbs, rung by rung, and what each one demands before it will evolve - the number half this game's mission goals are written against.

Mechanics

The walker model -> Every Impressions city runs two opposite systems at once. Employment is a global pool with no geography in it at all. Services are delivered by a person who walks out of a building and covers whatever they happen to pass. Almost every frustration these games produce comes from expecting one of those to behave like the other.

Production

15 producers -> Every chain from raw material to finished good, read out of the engine rather than timed with a stopwatch - with the rate it steps each workshop's progress bar with, where the source states one in a shape this page can stand behind.

Campaign

20 missions -> Every mission across eleven ranks, with the peaceful and military province each rank after the second offers you.

Cheats

13 codes -> Every documented cheat code, and how to trigger it - save-file byte offsets for the two games that predate any cheat box, and the Ctrl+Alt+C codes the later manuals never mention for the rest.

Open-source engines

Julius Foundational — base of the lineage
Active

Built by Bianca van Schaik

C (SDL2)
Windows, Linux, macOS, Android, Vita, Switch
100% — byte-identical goal, saves fully compatible with the original
First release Nov 2018 · actively maintained

Last commit 34d1ecd

Repository ↗ Website ↗
Augustus Fork of Julius
Active

Built by Keriew

C (SDL2)
Windows, Linux, macOS, Android, PS Vita, Switch · browser build
One-way — loads Julius/C3 saves
Most active dev community · hosts a Discord

Last commit b7d8ee1

Repository ↗ Play in browser ↗

How to play it today

Every engine above needs a copy of the original game. They ship code, not assets — none of them is a way to play Caesar III without owning it.

Sold on both stores. Either copy supplies the original data files Julius and Augustus read.

Tools & Mods

  • Map Editor (map & scenario editor) Tool The official si_caesar3_mapeditor.exe, bundled since the v1.1 patch (mentioned above) - not every surviving copy of the game still has it, so this ModDB mirror is here for whoever's is missing it. By Impressions Games
    Map Editor (map & scenario editor) ↗
  • Julius / Augustus editor (built-in) Tool Not a redistribution of the file above - a from-scratch reimplementation of the assignment editor, built into Julius's own menu rather than running the original .exe. It still needs the original editor's font and graphic files, the same way the main game needs original assets; this wiki page mirrors those per language. Augustus builds on it with Scenario Events - XML-scriptable conditional logic a map maker can attach to a scenario, e.g. "every 6 months, if favour is high enough, raise a good's trade demand." By Bianca van Schaik / Keriew
    Julius / Augustus editor (built-in) ↗
  • HeavenGames — Utility Programs Tool Fan-made utilities alongside the scenarios and completed cities - a desirability calculator, an .sg2 image extractor, a .map terrain explorer, save-file scripts. None are individually catalogued on this site; browse here instead. By HeavenGames community
    HeavenGames — Utility Programs ↗
  • ModDB — Caesar III Tool A fan-restored cinematics pack, a housing-requirements tweak, and a WSGF widescreen mirror, as of writing. By ModDB community
    ModDB — Caesar III ↗

Manual

Caesar III manual (Impressions Games / Sierra) -> Scanned copy, Internet Archive.

Community

GOG forum — Caesar series Active
GOG

GOG's own discussion board, shared across all three Caesar titles since GOG sells them as one series listing.

r/impressionsgames Active
Reddit

Covers the whole series in one place. Reddit blocks automated fetches from this machine, so its traffic level wasn't independently checked before adding it — the way MobyGames and a few other sources are handled elsewhere on this site.