Located in Mexico, right next to the border to the US, it is the single most visited border city in the world. Also, it's not as shitty as those cheap, stereotyping American films would have you believe (read: it's not composed of a bunch of dodgy bars and whorehouses and a tiny police office).
Rather than have a long central vein and then nothing around it, as another poster described, it is a diverse, large city; and like every other city of its size, it has its good and bad neighbourhoods.
Sure there are parts of the city where crime is high as fuck and the conditions are practically unfit for human life, but hey, Mexico is considered a third-world country for a reason. Besides, there are also the "nicer" neighbourhoods, which pretty much look like a first-world suburb (and no, it's not just the narcos that live there).
I'm not surprised the other posters are entirely unfamiliar with that last part of the city, as they probably only visit or know of the first one; which is, sadly, the one that draws the tourists in.
Today I found out that Tijuana isn't just some fucking crime spot.