Saruman's Pits

[Mithadan]

Perhaps this is a matter of Saruman enveiling the reality of what had happened to Isengard through the power of his voice? By engaging with Gandalf and attempting to convince him of the rightness of his position, he distracted Gandalf from noticing what had actually happened at Isengard. Saruman's power of persuasion and the use of his voice appears to be among his greatest powers.

[Legate of Amon Lanc]

I have nothing against the illusion idea, but I think it is perfectly unnecessary. As some have pointed out, it seems that the pits were not necessarily visible upon approach. Add to it the fact that Gandalf arrived in haste, barely passed through the gate (upon which the inexplicable sense of dread fell on him, which might have contributed to his distraction), and right after that he starts talking to Saruman, which distracts him further (plus, add the possibility of the Voice being used to shift his focus more on the talking and less on looking around).

Also, correct me if I don't recall properly, but I believe Gandalf says that he arrived at dusk, or maybe even after dark. That would severely limit his powers of observation. I mean, riding up the road rimmed by some newly-raised iron columns and whatnot, in a large area encircled by a wall, in twilight or even at night, you don't necessary see any pits which are, say, couple of hundred meters away from you.

So I think it is the combination of all of the above (except the illusion). Strategic placement of the pits that they are not right under everybody's nose when they arrive. Limited visibility after dark. Gandalf's mind preoccuppied by "what are we going to do about the Ring?", "the Nine are abroad!!! We're doomed!!!", "I hope Frodo is still alive", "oh no what if that fool of an innkeep didn't send my letter? I'm gonna fry him" and "oh no, I have to make this arrogant colleague listen to me and endure his wannabe-intellectual condescending comments before we get to the heart of the matter". Saruman's Voice as a bonus. I don't think we need more than this to explain that no pits with Orcs were visible when Gandalf arrived.

And yes, Saruman had to be at the breeding for decades, basically it would be sometime after he had locked himself up in Isengard after looking into the Stone. That still gives him a plenty of time, plus we could think about some accelerated growth for the Orcs (I don't mean cocoons, but since these were basically meant to be killing machines, and Orcs breed fast anyway, I am pretty sure you could have them reach physical maturity in several years instead of two decades).

[Inziladun]

Originally Posted by Legate of Amon Lanc

So I think it is the combination of all of the above (except the illusion). Strategic placement of the pits that they are not right under everybody's nose when they arrive. Limited visibility after dark. Gandalf's mind preoccuppied by "what are we going to do about the Ring?", "the Nine are abroad!!! We're doomed!!!", "I hope Frodo is still alive", "oh no what if that fool of an innkeep didn't send my letter? I'm gonna fry him" and "oh no, I have to make this arrogant colleague listen to me and endure his wannabe-intellectual condescending comments before we get to the heart of the matter". Saruman's Voice as a bonus. I don't think we need more than this to explain that no pits with Orcs were visible when Gandalf arrived.

Good points. I think my main opposition to the camouflage theory leading to the "strategic placement" of the pits is the question of exactly who Saruman would have had in mind when planning how to hide them.
Who went to Isengard? Really no one, apart from Wormtongue. I get the impression that Gandalf and Radagast had not been there for quite a while before the event in question, and they only went because they were summoned. I don't think Saruman would have been worried about the Eagles seeing what he was up to, because before imprisoning Gandalf he was a known ally, and no one would have been watching him.
So, how much trouble would Saruman have been inclined to take to conceal his pits and forges? In his pride, too, he may have thought he was naturally smarter than the rest of the Wise, and have not thought them a source of worry.

[Zigûr]

Originally Posted by Inziladun

no one would have been watching him.

Sauron perhaps?

I'm inclined to agree more with mundane disguises being used personally, to connect with his "mind of metal and wheels".

Legate is correct as well; Gandalf arrived after dark:

'Late one evening I came to the gate, like a great arch in the wall of rock; and it was strongly guarded. But the keepers of the gate were on the watch for me and told me that Saruman awaited me. I rode under the arch, and the gate closed silently behind me, and suddenly I was afraid, though I knew no reason for it.'

It would have saved me a lot of time thinking about this if I'd checked slightly further back in the text. Happens to me all the time I feel.

[William Cloud Hicklin]

Moreover, it's in the nature of pits that they're hard to see unless you're close to them or on an elevation. Even minor declivities-- just ask William Prince of Orange.

[Nerwen]

Look, I believe some people are over-complicating this. Surely Saruman's pits and things could just happen to be out of the line-of-sight of Orthanc's "front path" without him having taken any great pains with strategic placement, let alone magical concealment?

[Galin]

Even traitors respect curb appeal!

Anyway I, at least, try to keep my pits hidden... hidden in bigger pits if I can find them! It's a good thing.

[Legate of Amon Lanc]

Originally Posted by Inziladun

So, how much trouble would Saruman have been inclined to take to conceal his pits and forges? In his pride, too, he may have thought he was naturally smarter than the rest of the Wise, and have not thought them a source of worry.

That is one thing, I agree with that. As for whom he would have in mind, if he actually had anyone, when thinking about concealing the pits, then in the earlier stages (few decades back, when he started), he would perhaps still think about envoys from Gondor or Rohan. Not that any had been to Isengard in decades, from what we are told. And Saruman had "sealed himself" in Isengard after the Ithil-stone incident, whatever is that supposed to mean exactly; in any case, it probably means cutting off contact with the outside world. "Iron Curtain", if you will.

Most people would not come to Isengard anyway, even if we imagine e.g. a bunch of Rohanian envoys who managed to get ambushed by Dunlendings, got lost in the wilderness, are in the middle of the storm and looking for shelter somewhere in that area: given common folks' general superstition, they would think "oh no, that is 'sorcerous valley', let's not go there, my aunt used to say you might turn into frog if you only drink water from one of the springs around it! Let's rather find shelter somewhere else."

But, I mean, Saruman could still keep "strategic placement" of the pits in some way. In the latter stages, however, he probably didn't care and would think himself so powerful that he would rather intimidate his enemies. But Gandalf was basically about the only person in Middle-Earth he would want to fool (and okay, Radagast. But we don't even know whether they met in Isengard personally or whatever).