Yes, they're called Structural Terra Cotta. They are lightweight and hollow inside, and yep the grooves are to help adhere plaster and stucco (you wouldn't normally see these tiles in a finished building).
Yeah I was alone on this particular night; not really worried about vicious animals on Staten Island, and the benefit of being there at 4AM is that most people are fast asleep.
The colony has always been kind of a low key place in my mind; if anyone is there, it's usually some bored teenagers. I would keep an eye out for stray paint balls during the day though!
I think it all just comes down to money. Detroit is bankrupt (in debt by an astonishing $18-20 billion dollars), and selling homes to people who can't pay the property taxes or fix them up would just cost more.
@ Freespirit - I don't understand it either. Look at Detroit. Blocks and blocks of vacant houses just left to rot or become the victim of arsonists. I know there are circumstances like the economy and the area, but after these houses go through foreclosure, instead of just letting them sit vacant to eventually be bulldozed, why don't the sell them dirt cheap to people that are homeless or otherwise destitute. If they sold these houses for ten bucks, I'm sure they would draw people to buy them. Maybe make conditions like you have to live there for so many years. I don't know, I just think something should be done instead of just letting these places just rot away until all that's left is an empty field. I look at street after street in sections of Detroit and other cities and see these huge, once beautiful houses falling apart, half burnt or what have you. It's disgusting that this happens in this country.
I think I read somewhere on this site that he only does this with people he trusts his life with or else he goes alone. Which is probably how I would feel about it. I sure wouldn't want to explore places with a bunch of yahoos!
Yup the bent thing on the right is a poor little sapling.