So...I've finally settled on a name for my kingdom and it's named Azurite. It's a modern, fantasy kingdom inspired by America and Europe, mostly Great Britain, Wales, Scotland, and Ireland. However, I'm terrible at when it comes to describing capitals since this is my first time doing this. The capital of Azurite is Selenite, and it has today's technologies, with some Victorian/Edwardian flair to it and this is a parallel universe of ours, even though there has been darkness in the past, some has still managed to find it's a way through, but other than that, people treat one another with kindness and respect, though they are human beings and not perfect. Some of the citizens have personalities that have those in real life, such as movies and TV shows, except the characters I create have personalities that are mashed in together, like John Smith from Pocahontas and Jack Dawson from Titanic. The homes have both a traditional feel and a slightly modern one mixed with other buildings such as schools in Elizabethian, mixed with a Rococo flair, and churches have the Gothic revival look. As for fashion, it varies. There are outfits taken inspiration from the Victorian/Edwardian period where it is mostly dressed and such. The younger generation prefers jeans and shirts, while some stick to tradition and add their own taste to it to keep up with the trends on social media.
Well, I'm not an expert on city planning, but I live in Europe and most cities here have a city core that stems from the shape of medieval cities. They were roughly circular and enclosed with a city wall, which had several city gates. My home city, for example, has a core that you can traverse on foot in about 15 minutes, so it's roughly 1km in diameter. The former city gates have been continued by large streets into the cardinal directions and the former city wall has been replaced by "the Ring", a wide, high-traffic street that guides the traffic around the inner city. For a city as you describe it, I would choose a similar shape with wide boulevards. You can have trams or horse carriages on them, depending on taste. My city, as well as other German cities, like for example Berlin, also has a lot of very nice "Gründerzeithäuser" - houses that were built by rich citizens in the 19th century. Back then they often housed one family with their servants, but there were also tenant houses and even the bourgeoisie ones were later refurbished into rental houses with one central staircase and two apartments on each floor. Just google "Gründerzeithaus" to get more pictures. In medieval times there were already different districts in cities to separate unpleasant trades (dying & tanning, for example) or "undesirable" populations (Jewish people) from the rest of the city. This practice was expanded in the time of industrialization, so that you can find entire city parts with only industrial architecture. Or you have these nice gas reservoirs. Look up "19th century industrial architecture" to find more pictures. Basically, I would recommend you find pictures of buildings that you like, for example by going to pinterest and searching for "19th century architecture" and then you try to describe the buildings according to what you see on these pictures. Which shapes do they use, which materials, which colours, which ornamentation? How wide or narrow are the streets, are there trees, benches, little shops or no, public transport, cars, coaches, sideways? How are the people dressed etc. How does the city smell? Is there smog? How is the weather? What do you hear? Trains? Cars? Horses? People shouting? Are there parks? Where are they? Are there attractions for the folks to be entertained? Oh, here is a nice park from the 19th century with view on a 19th century historicist tower and a 1972 representative high-rise. Yeah, have fun.
I think QueenOfPlants summed up most of the important things pretty well, but as someone whose parents made living by guiding tourists through cities, I feel obliged to add a few points. First, the shape of a city is usually dependant on what economic function it serves. For most of my life, I lived in Poland, so I'll use the cities from this small part of the world as examples. Warsaw - the Polish capital - is built on a rectangular plan. There is one central building (Pałac Kultury) and around it are four big streets, creating a rectangle. The reason for this is that most of the city was destroyed during world war II, so most of its architecture is contemporary and build with the needs of modern people in mind - streets are wide and the city center has plenty of service-based buildings. There are also a lot of concepts borrowed from modern cities, like skyscrapers - the city can afford it, since there are little to no pre-20th century structures, meaning there's plenty of space to use. In comparison, Łódź has been relatively unharmed by the war, and it's one of the most archaic cities in Poland. The streets are unbelievably cramped, trying to get anywhere using a car is a chore, and some roads are still made out of bricks instead of asphalt. It's a beautiful city, full of buildings from the 16th, 17th, and 18th centuries, but living there is a logistical nightmare. It's simply unfit for modern people. My favorite, however, is the Tricity. For years, this was Poland's main port, and its structure is very interesting. Most cities generally grow in all four cities of the world, but Tricity only grew in two - western and eastern. That's because its entire economy depended on the sea, so every major building/structure had to be built relatively close to it. Nowadays, you can ride through the entire Tricity by only going straight through the main road, and you won't miss a single district. The most popular fact about cities, in general, is that they are usually built next to a big river to simplify trade, but economics can have other silly effects. Kraków was usually known for trading horses, and to this day, it's known to most as "that one city that smells like horse sh*t". I think it's important to write down most of the historical context for your city - were parts of it destroyed by wars, what was it known for, why was it built here, etc. Especially if the city is supposed to be old - then the most important factor influencing its growth was probably economics and politics. Modern cities are built more with the comfort of the citizens in mind. And yeah, checking out some pictures on the internet is sure to help. Also, if it's an alternate reality, keep in mind this world is probably much different than ours in terms of culture. For example, the modern concept of historical preservation was largely influenced by Victor Hugo and his "Notre-Dame de Paris", and that novel was inspired by dozens of french revolutions that caused hundreds of important, historical monuments to be destroyed. Not every culture values its architecture as much and might demolish some of its outdated buildings to suit the needs of contemporary citizens.
A fantasy city is a contradiction in terms. We have cities in the real world, and in fantasy books they are most often a place where the reader's mind's-eye is re-centred in the familiar before the fantasy takes off again. One approach might be to consider everything about the city malleable and only write into it the plot devices the story needs, and the purple passages the characters need (for example if a 'chosen one' has grown up on a farm and the city represents society's validation of him/her, there's traditionally some kind of reaction shot of going through the gates)... but if the city can be bypassed/minimized in favour of things the reader can't see by looking out of the window, this approach would say to mention it without going there. I'm not a huge fantasy reader, in my life I have read a couple of dozen big, obvious, popular series. What strikes me though is that the cities really haven't stood out, or left much of an impression on me. The City of Destruction and The Emerald City are important ones, but after that there's a real big drop-off... Minas Tirith has a big wall round it. So does Troy. Ankh Morpork has a dirty river. Mildendo has awful bureaucracy. Hamelin has a rat problem. So does London (in James Herbert's version). Trantor is sci-fi, Sigil is originally/primarily in games, and Gormenghast is a castle with some city-like qualities... I can't form even the slightest mental image of Tar Valon. Millions of fantasy-citizens in the Belgariad, The Chronicles of an Age of Darkness, Prydain, Narnia, Cimmeria, Pern, The Death Gate Cycle, The Deverry Cycle, Helliconia, The Chronicles of Thomas Covenant, and Memory, Sorrow, and Thorn - have vanished into the ether. All I can say is: try the mental exercise - I doubt I'm alone in recalling characters and plot points more than cities and I'd suggest it's because they're only apparatus, a means-to-an-end. And to a great extent, I think the memorable cities work because they are inhabited by memorable characters. The City of Destruction doesn't even have a description passage - we first see it through Pliable and Obstinate, the servants it sends to bring the MC back. If the OP's city is mentally-based in the modern, real world, I'd suggest to establish all of its fantastical elements in a few paragraphs early on - in case the reader don't realise there will be some fantasy and gets into thinking of it as a normal city. But once that's established so they won't forget, it should be safe to leave them with whatever their own mental images are of a modern city. There won't be any credit for reinventing the wheel by describing London or New York in competition with all the writers who have ever lived in them.
