6. Dunwall - The Dishonored Series
The Dishonored series has taken a lot of inspiration from the Thief series, including it having a great city to explore. The Dishonoured series takes it even further though by having two great cities to explore (what will they think of next)? Whilst Karnaca from Dishonoured 2 is pretty great the better city is clearly Dunwall.
Dunwall looks very much like a steampunk version of London that runs off whale oil and is definitely in the category of video game cities that you would not want to visit in real life. Plagued by... well the plague, Dunwall is swarming with illness spread by disease-carrying rats that are all too happy to bite your face off if you're not being careful. A huge class divide is present in Dunwall as well leading to the poorest getting infected by the rats whilst the richest can afford the medicine required to stop themselves from getting ill. But as bad as this city seems it is a very fun place to navigate and murder your targets, which in a Dishonoured game is all you could ask for.