What's the main reason

The main reason the narrator wants to visit the pit at Aldgate is his innate curiosity.

I went all the first part of the time freely about the streets, though not so freely as to run myself into apparent danger, except when they dug the great pit in the churchyard of our parish of Aldgate. A terrible pit it was, and I could not resist my curiosity to go and see it. As near as I may judge, it was about forty feet in length, and about fifteen or sixteen feet broad, and at the time I first looked at it, about nine feet deep; but it was said they dug it near twenty feet deep afterwards in one part of it, till they could go no deeper for the water; for they had, it seems, dug several large pits before this. For though the plague was long a-coming to our parish, yet, when it did come, there was no parish in or about London where it raged with such violence as in the two parishes of Aldgate and Whitechappel.