It's possible they like the acoustics. If the area is minimally used and/or minimally furnished, their voices may bounce around in a way that's interesting or pleasing to them, so they head down there to make noise and listen to it. During some renovations where rooms were emptied out here, my cats would frequent the empty spaces and yowl while in them; the behavior stopped when the rooms were re-furnished and the echo stopped.
It's also possible there's a sound generated in that area that you don't hear (as you don't frequent that area), but they do; the sound may be interesting or distressing, and they're responding to it when they go into that part of the house. It might be an electrical sound, a pest in the walls or one of the rooms, or something else.
Or it may be a visible pest (insect or spider) or other stimulus (light) that you aren't noticing due to not frequenting that area; if they want to "hunt" it, and can't reach it, then they may be yowling in frustration at not being able to access the area. Mine often go nuts over reflected lights and pets near the ceiling.
Or, if the doors to those rooms are closed, it may just be natural cat curiosity, and they want to go through that door. Again, this is something I see in my own cats regularly; I have two rooms that are closed off from mine, and at least once a day I hear a cat "yelling" at it and trying to get in.
To address the issue, you'll need to inspect the area, preferably at a time when the behavior is happening. Look and listen for each of these options (and understand that you may not be able to hear or see what they do, as their hearing is more sensitive and their vision more attuned to spotting "prey"). Watch for the patterns triggering the behavior--is it a particular time of day? Are they sitting in a specific spot or looking in a particular direction? By observing both the cats and the area, you'll be able to determine the stimulus causing the yowling, and reduce or eliminate it.
