Here's a view directly from above, encompassing all the ruins. The 'rooms' cover the peak, at the top of the photo, and from there spill down to the small plateau below it. North is to the right.
Here's a view more from the side, which shows how the rooms progress down from the hilltop. (If you like, you can always download the enlarged view to get a higher rez image.)
Not only are there many rooms on many levels, there is also terracing, held in by rock walls, that added level ground near many of those rooms –some of that terracing can be seen on the right side.
A view from the top, off to the east –the ruins had direct line of sight to the entire Lower Verde area. (There's an area 'line of sight' map on an earlier post.)
The rooms themselves were very well built, with flat walls and square corners...
... and there are a lot of high-quality pottery sherds, all of which makes me think "luxury resort" as much as "lookout" –the home, I suspect, of some very important people.
Like almost all the forts in this area, I could find no petroglpyhs. But there are the mysterious "cupoles", as in this photo. Any ideas?
One of the myriad mysteries surrounding the ruins in this area is just what purpose the Boulder Creek fort served, and, most importantly, for whom it served that purpose.
But keeping with Wilcox' famous "Lower Verde Alliance", which posits, first, a longstanding conflict between the "Classic" Hohokam of the Phoenix area and both the Agua Fria community and that of the Lower Verde, and. second, a defensive alliance between the two against the Hohokam. The many hilltop forts can then be assumed to be lookouts, patrolling for encroaching enemies from the south and capable of signalling warning to one another over vast distances. Assuming, of course, that they're all contemporaneous.
Considering the architecture of the Boulder Creek fort, a lookout seems to me as good a fit as any. Compared to its sparse buildings, nearby Indian Mesa (which is not at all within sight) is a posh resort. There is clearly a multi room ruin on the hillside near Boulder Creek below (perhaps where the lookouts stayed when not on duty?) but, from what little is left of it, it's not as finely built or as complex as Indian Mesa's ruin.
In any case, here's a line-of-sight map from this Boulder Creek fort, including the several ruins intermediate, which can see each other as well, including a string of them between the "Pepsi Cap" fort, the "Cline Creek East" fort, and the Elephant Mountain fort far to the east.
Not shown is the "Henrie" fort, located on the south tip of Black Mesa, which had line of sight with both the Squaw Creek fort and Pepsi Cap. (The names of these places are, unfortunately, quite fluid.)
Far above the Agua Fria plateau and all the forts on Perry and Black mesas is this fort/lookout in the Bradshaw mountains to their west.
Since most of the forts on the plateau did not have line-of-sight with one another, I'm theorizing that it was meant as a communication tower for warning all the plateau residents –assuming it was built at the same time. A signal from the Henrie fort down on the plateau, which was on the lookout for anyone approaching from the south (where the plateau's assumed enemies lived), could immediately be relayed to the entire plateau from this point.
A photo of the trail to that fort, atop the peak ahead...
...and here's a drone photo of that fort from above.
There's a large walled area at the top of the peak, perfect for securely relaying smoke or fire signals, and off that what looks like sleeping quarters, attached to the right with a narrow doorway. Above that is another room which I never could figure out how to get into.
The view of the Agua Fria plateau and all it's forts, from the Bradshaw fort –it's the area covered with dried grass in the photo. (It may even be visible from the Polles Mesa ruin, 40 miles to the east.)
