From the River Journal Blog
Let’s look this time at the tunnel half of the equation. After all, if there were no tunnel, there’d be no trail. But first it should be noted that the Old Croton Aqueduct, for much of its length, is basically “cut and cover” construction. No sweaty sandhogs bored tunnels hundreds of feet underground, as with the New Croton Aqueduct. No, when you walk or bike the Aqueduct trail today, the stone and brick conduit is just underfoot.