It was declared that no arch so flat could remain in place with mechanical aid of some sort, an it was alleged that there was a concealed beam or plank running though it.  When the ruins of the church began to be removed in 1913 and the arch was examined it was found to be a genuine construction of masonry, and not a fake. The Panama Gateway – Joseph Bucklin Bishop 1913

Much interest centers in the old Dominican Church at the corner of Avenue A and Third Street, because of the Flat Arch, fifty feet wide, that spans the portals.  The woodwork of the church was burned in the fire of 1756 and was never rebuilt, but the flat arch still stands and the quaint legend that attaches to it is interesting.—The friar who was directing the construction of the church had the arch built as we see it standing, but it fell; a second effort was made to erect the arch and it fell again.  It was then that the friar prayed for guidance.  In a vision it was revealed to him just how it should be constructed, and so he placed the stones with his own hands just as we see them today and achieved an architectural triumph for it has remained intact, resisting earthquakes and time with no support other than the terminal arches, which fact has puzzled practical architects from all over the world.  This old arch also played an important part in building the canal, for the reason that it had remained standing all these years was convincing proof that Panama was outside of the earthquake area, and this fact was a deciding factor in the momentous question of building a lock type canal when the question was being debated as to the feasibility of a sea-level or lock type.  Picturesque Panama by Jean Heald 1928 

The flat arch collapsed on Friday night, November 7, 2003.  This is truly a terrible tragedy for the county of Panama.  I hope this presentation will help preserve the Arco Chato at least in memory.