We have known for a while that part of our basement floor has a small dip in it. It was occurring to us that the dip seemed to be getting deeper very slowly over the last 7 years... Well, we finally emptied and moved the furniture, ripped up the carpet and took a look.
Ripping carpet was fun. Discovering that the dip covered half the floor and was much deeper than we had thought... not so much!
On the positive side, whatever cavern has developed beneath our house has not affected our foundation.
On the more positive side, such things can be fixed either by breaking up the floor, filling the space with gravel and then repouring the floor, or by a process called mudjacking. (How would you like to tell your parents that you've decided to take up mudjacking as a career? It actually involves drilling holes in the floor and filling the space with pressurized concrete "mud" which then "jacks" up the floor.)
On the negative side, do either of those procedures sound cheap to you?
On the amusing side, we asked the kids what they thought we'd find when we ripped up the carpet and Leena answered without hesitation, "Bugs, mostly lobsters." Regardless of the arthropod confusion, we found neither bugs nor lobsters, just 1960s era checkerboard linoleum tile. And a big dip.