Whilst escorting a certain pair of NPCs to a certain Blades stronghold, we came upon a walled and gated city. I don't recall the name, but I believe it started with a 'B'.

Upon reaching the city gate, I attempted to activate the gate without dismounting my steed. Unfortunately, the result was that the city interior was loaded and I found myself dismounted and my horse, as well as those ridden by my companions missing. Exiting the city gate revealed that the horses remained outside.

I had intended to ride through the city to reach the aforementioned Blades stronghold (in hindsight, I'm not really sure that the city in question had two gates, so assumption on my part) but ended up riding around the city because I wasn't sure how to get the horses through the city.

So, are horses not allowed inside cities? Or how does one manage to ride through a city in this sort of circumstance?

You can't take horses into cities, sadly. It's possible in a modded game but not in the vanilla (or un-modded) game.

Thanks Shelly, you seem to keep coming to my assistance. I do appreciate it...