Bricks, Masonry, Asphalt and Concrete - Filled-in basement window well

Hi there. I just moved into a house that has a basement window well, or maybe it used to be a full walkout, partially filled-in and then covered on top with some slate slabs. I thought it was just a window well but I think it may be a full door. It appears that there is some old rotting plywood over where the opening used to be. There is a finished bathroom on the inside, with no window or other signs of a previous opening. I would like to fill it in the rest of the way, and get some more usable space outside, but I am kind of nervous about what looks like a shoddy cover job for the old opening. What is the right way to do this? Is there any good option besides digging it back out and bricking/cinderblocking up the opening? Can I use wood at all or is that a bad idea since it will be buried?

Thanks for any info.

Will

Wood is a very bad idea since it will be buried. It should have been blocked up. If you plan on digging it out, replacing the rotton wood, at the least get some pieces of peel and stick ice and water shield membrane to put on the wood. It won't seal it competely, but it will help.

Thanks for the info, I figured as much. Will see what I can do...

You might also check to see if a permit was pulled to close this window/door and whether or not the code requires that it still exist. Many times inhabited basement areas are required to have a minimum number of windows or doors for escape.