What even is that? Did they carve a mountain over time and turn it into a city? How long would that take. Who would start with that, considering it is also an island of all things? Well whatever.
Scoring scale 4-10
Feasibility: 5+. While it is a lake city, you usually build those on the shore and not on an island. Atleast you wouldn't have to travel to a quarry, since your city is built on one, provided the stone they cut is actually useable and not some trash minerals. Water access is easy, but what about food? There is no sign of ports in the city and no sign of surrounding farmland for that matter. Well the farms might be off screen for all we know, so that can be partially be forgiven. Nonetheless, how would you start this whole thing? First settle on the
mountain and then start building the bridges? Build the bridges to a mountain and then start carving the city? Mayhap this was a quarry in ages past that got turned into a city as they hacked away at it, but even then, you'd most likely live in the city they built from this mountain not on this mountain.
Defensibility: 8+. Narrow bridges with only two main access points and even with that, the whole city is surrounded by a sturdy wall, with towers covering the walls and each other. Assaulting this would be a nightmare of logistics and defensive wet dream of any good general. One can imagine what a grapeshot or a similar spell could cause on those bridges. Even if the gates or walls are somehow taken/breached, the layering of the city serves as additional walls. This is essentially a Minas Tirith, but even more of a nightmare to counquer. Additional bonus points for having the royal palace/fort be a separate entity from the main city, so the actual strong point and place of importance is even harder to capture.
However, it seems to be extremely dense, so I don't think this city would fare that well in a siege. Not to mention, the lack of ports and just two easily blockable access ways, the sieging army barely has to try. Should the food stores be insufficient, I don't think you'd have to wait long for the city to devour itself, maybe even literally so. Moreover, destroy the bridges and any defending force inside is trapped and completely eliminated from the war. No need to bother with assaulting or sieging the city at that point.
Also, the towers are quite a distance from each other, so manning and securing the walls effectively throughout the day might be difficult. I can imagine some sneaky swimmer-cum-climbers scaling the wall and then torching say the food stores as an example in the cover of the night.
Also also, the palace and the city can't really support each other. If one is taken somehow, it becomes a strong point for the attacker to use as a staging ground for assaults on the other.
General design: 6. I like layered cities. I like segmented cities. This is both. The very top of the city-cake probably has a view to die for. Makes you wonder if the higher you go, the more affluent the people are or maybe they subvert our expectations and the slums are actually on the top layer. It is lacking in decor, monuments and stunning buildings. Aside from the palace, it just is a city-cake. No big temples, towers, barracks, arches, statues or any of the bread and butter of fantasy cities. Definitely loses points from that. The bridges too are quite dull. Slab some statues of past monarchs and whatnot on them. The top layer of the cake most definitely should have a grand temple or palace or something
GRAND there. Also it's not just a waterfront city, but a lake city and it completely lacks any harbours or ports. Additionally, there should be another gatehouse or a check point on the other end of the bridge, those things really are so dull and boring looking.
Final score: 6½. Interesting idea, but very bland realisation. Not to mention that an impregnable fortress is made completely moot, when you can just sit safely fishing on the otherside of the lake and watch your enemy starve in peace. The longer I look at it, the more disappointed I get. At least it has a good view and you could easily build a skii-ing slope inside the city.