There were a number of wondrous inventions created centuries ago, some of these were not recreated until the 19th or 20th centuries. While most of these brilliant inventors were from my hometown of Alexandria (hence my initial interest), there were others from Rhodes, China, or the Muslim world.
Heron of Alexandria was the inventor of the steam engine (his "wind ball"), odometer, cheiroballistra (early large weapon--later used by the Romans who were never able to create a more advanced version), dioptera (remarkably similar to the modern theodolite of surveyors), & numerous automata. One of these was the first robot: it was a full play-in-a-box, that rolled itself out onto the stage, offered music & sound effects (instruments & additional items, such as a thunder machine, also created by Heron for this device), moved "actors," changed backgrounds, rolled off of the stage at the end, and reset itself for the next performance. Many of Heron's devices had clever self-regulating feedback control devices (such as the self-trimming lamp) that formed the basis for modern cybernetics.
Yet another remarkable ahead-of-his-time idea is that of sequence control, or programming. He was able to craft devices that could control the timing and sequences of actions indirectly, without any direct control. For example, he would wind a cord in a specific fashion around an axle studded with pegs. As a weight pulled the rope, it would unwind and pull the axle in different directions at precise times. This in turn would be the main power for a series of gears that would be engaged, activated, disengaged, and reset, according to the motion of the axle & timing sequence.
Supposedly (no artefacts or diagrams have been found), Heron created devices that could speak, and others that could record sound.
Archimedes was considered such an ideal thinker that the story of his death became something of a parable. His inventions were perhaps even more numerous and remarkable than Heron. Where the Alexandrian inventor was more focused on remarkable gadgets, Archimedes thought big. He crafted numerous war engines, each more terrifyingly effective than the last. One of these used mirrors to direct the sun's energy at enemy ships. The radiation would burn the ships within seconds (wood, not just sails, as these were furled during an attack) at a distance greater than their archers could retaliate. His "iron hand" could move or destroy ships. He is also the inventor of the compound pulley, and may have invented an early camera.
These are just two of the great inventors of antiquity. With their ideas extrapolated (instead of just the military ones captured by the Romans), there could be an entire genre of Bronze Age Steampunk developed.
Imagine articulated bronze limbs--with their own feedback system for ease of control from Heron & incredible strength from Archimedes, Archytas's flying machine, Ctesibius's hydraulic systems, Antikythera computers (based on an astronomical device that used a differential gear & far greater degree of precision than was thought possible prior to industrialisation), and giant clay & iron monstrous mobile statues marching about the land. The very lack of certain technological developments forces even greater cleverness in design. The possibilities are truly endless.
Development of these ancient ideas into a fantasy campaign works, even outside of their contemporary setting. I have employed some of the ideas, inventions, & principles, into Midian's steampunkish elements. Thus far, it's worked quite well. Of course, as a potential niche genre itself, Bronze Steampunk would work great in its proper ancient setting.