The roadway to the fort has a sharp bend at the end and the entrance doors have giant spikes on them. In the event of elephant attack the elephant would not be able to get up lots of speed on the run-up and I believe for whatever reason elephants have an aversion to giant spikes... I forget why.
The guide told us there were two motes surrounding the Agra fort. The first was of crocodile infested water. The second was a pit of lions - since getting back I have found no information corroborating it but it would be very cool if it was true!
The photo shows your handsome and compelling protagonist (which you have gained new-found respect and admiration through the course of his travel journal) on one of the Maharajah's thrones. The giant crack in it is actually where a British war ship hit it with a cannon ball. You can still see where the ball ricocheted off the throne and went into the wall to the side of it - awesome!