Mud nest tubes made by the Organ-pipe Mud-daubing Wasp (Trypoxylon politum). I’ve been finding a lot of old ones, from previous years, the ones with holes in them. Tucked out of the rain, especially in the nooks and crannies of mausoleums in Green-Wood and the tunnels in Prospect, they can last a few years.
I have rarely seen the wasps. Unlike the Yellow-legged Mud-dauber, they’re pretty elusive.
Backyard and Beyond 
I love the idea of a giant insect hotel for a mausoleum!