You can look in ravines behind old cemeteries though...being observant of trespassing regulations of course.
Ravines behind old cemeteries??? We might have some canals nearby some of ours but I'm not sure that counts as a ravine. LOL
You obviously haven't ever been to New Orleans famous old cemeteries... where almost everyone is buried above ground. If you dig 6' under down here and you might strike water. There are a couple of areas in the metro area where they have in ground plots in the areas that are on high clay ridges... the same areas that didn't get flooded during Katrina.. but even in some of those areas, they use above ground tombs.
Here's my family's plot in the Lafayette Cemetery #1, right across the stree from the world famous Commander's Palace Restaurant. Even our family plot is above ground but you can see all the tombs in the background.
http://www.lafayettecemetery1.com/2_abc/2_a_b.htm
Unfortunately, some criminals stole the brass plates for my relatives with my last name and I didn't even realize it until I saw my family's plot online and realized my mom and dad weren't listed.... because the folks that set up the website used only the information found on each grave plot or tomb to list who's buried in the tomb. I've been trying to get them to update the information for months to no avail so far.