I agree with IronyOwl; more plot about the city is required. Basic questions such as how a city developed over time, what sort of people live there, their outlook on life, ect are quite important for building style. This will become increasingly important when we begin work on the lower class areas, as those are not designed so much as they are grown like a moss upon the aura of the city. At this point the directive for building is little more than 'sometime before world war 1 and after we stopped living in mud huts.'
I kind of have thrown to together a (very basic) plot in my head as part of the temple design process, it might be in line with what others are thinking. There are also notes on why I think this line of reasoning makes sense with the current city in brackets.
Several hundred years ago, seven settlers came to the city's grounds (as per the tombs in the temple main floor) from a distant shore by boat (why the temple is on the shore). They constructed rudimentary buildings and dug caverns for ores and materials, destroying old buildings as they went (hence why places like the Underhaven and Moria lack many permanent residences - they were dug and expanded for years until reaching their present state... and may even change again. And also why the town is such a hodgepodge of different designs).
As the prosperity of the city grew with the discovery of rare ores and metals, additional settlers arrived and expanded the city. It wasn't long until the wealth had attracted even great noblemen (original settlers of the 'high end' portion of the city, construction of the keep). However, strange and forboding prophecies came to be written about the city as it grew (the creepy signs in the quarry reed farm, the stuff I mention in the attic of the temple). But this did not stop the influx of many settlers looking to strike it rich (the development of the slums and the middle class area) - not all of them successful or pure-of-heart.
With time, the city grew to encompass a great stretch of land, straddling distant shores with vacation homes, refineries and deep mines (the spawn area, the quarry, building outside the city). Rampant growth encouraged dangerous practices (the great fire) but the stonework of the city and its guild of master craftsmen could withstand almost anything thrown at it.
[What follows I just made up now]
Within recent memory, great upheavals in technology have been accomplished - lighter than air travel (airships and balloons), artificial lighting (lightstone from the nether), and massive machinery and automation (I'm working on a forge design that I intend to make look somewhat automated, the question is getting all the parts to play nicely together - I think across the harbour, at the quarry for example, would be an excellent place to build huge industrial looking buildings). The city is rapidly responding to these changes, although much of the old character, architecture, and building design, is trapped underneath new, hastily constructed, technology.
Most of the people that originally settled the city were stoneworkers, miners, and metalworkers. They were joined by peasants, farmers, hunters, and great noblemen, mostly those involved in the mining trade. As the mines ran out of easily accessible materials, many workers were laid off and have become angry and bitter at their former masters and coworkers, some of whom have grown rich from their labours. Many more workers were crippled over the years and forced to stop working (this may provide a general feel for the slums). However, there is always someone looking to make a quick buck in the guise of 'helping' the worse-off.
Around the time of the many innovations, there were also a great deal of layoffs in the mine due to a dry-spell in mineral discoveries, which resulted in a riot in and around the keep. Soldiers fired on the crowd after being attacked from the inside, supposedly by the crowd although there has been no formal investigation. This resulted in the keep being redesigned somewhat, in order to prevent that from occurring again (the crenels on the inside). There is still some resentment among the older lower-class.
Master stoneworkers always have work - construction is always in demand, as are high quality crafts. Farmers and hunters have increasingly moved outside the city, but others have changed their trade to become bakers and butchers. The demand for these services is dropping over time as the amount of imports increases, but there will always be a market for them. Some of them are going out of business with the advent of faster transit, but they will be putting up a good fight.
Those who worked in the metal industries have seen a resurgence in their craft but have never really been out of work. Even if the mines ran dry, the other cities would send their most valuable ores to Eisenhauge to smelt and work, as many great craftsmen were, and are, in the city. This has also led to a continually thriving import/export business, along with the associated services (bars, hotels, shadier stuff). The most innovative craftsmen are now building forges and huge industrial mining complexes (but these marvels of technology need remarkably few employees...). Some in the import/export business are keeping up with the times as well and preparing for aeronautical ventures. Most craftsmen are either completely independent, funded by a decadent nobleman, or part of a collective of craftsmen working in the same shop.
The noblemen who ventured to the city are increasingly finding themselves out-of-the-loop and are becoming increasingly decadent. Only those who have taken an interest in the thriving businesses of the craftsmen are actually making money these days - the rest lounge about in their massive estates, writing angry editorials and letters to whoever will read them about the ungrateful lower classes. There are fears they will use their influence over other cities and their massive stocks of gold to impose their brand order on the city.
Soldiers in the city were mostly phased out over the years in favour of a sort of military police, with the keep nothing but a historical relic, except for the most dangerous of criminals who may be held somewhere in its depths. Officially they report to the mayor of Eisenhauge, but by decree following the riots, no one except the ruler of the realm can issue direct orders to them. However, even the ruler's ear must have a price. Whether anyone in the city can afford that price is debatable.
There is also a new class of citizens moving to the city - explorers and pilots seeking to use the city as a base of operations, or as another port of call. What their goals are remains to be seen. Most are merely visiting - a city with so much 'on the ground' doesn't interest them - although others are seeking to expand the sky-ward part of the city.
TL;DR: Industrial revolution era, history somewhat DF-esque. Not the centre of discovery of the newest technologies but they are arriving there daily.
Miners mostly out of work, lots of import/export, good metalworkers, decadent/out-of-touch nobles. Soldiers controlled by distant crown, act only as police/security. Incoming innovators with unknown goals.
Sprawling caverns the result of rampant mining, although most work ended a long time ago and resulted in unhappy miners.