What is this concrete slab in my front yard?

Question

House was built in 1964. Slab is about 3 feet across.

Answer 1

Most likely access to a septic system, or sewer sump.

Impossible to say for sure without gathering some hefty help and picking it off, or consulting old documents about your house. It covers something and was evidently meant to be findable and removable, but not easily removable (don't want kids falling in whatever it is.)

Or, the mid 1960's being what they were, perhaps there's an old fallout shelter under there ;^)

Standard Warning to not so much as stick your head in to whatever is under there without thorough venting, though you probably would not be so inclined for the most likely case.

If it's an actively used septic system, go ahead and have it pumped out, since that has obviously not been done in your memory.

Answer 2

My guess is its a Concrete Septic/Cistern cover. Try lifting it up, there may be a tank underneath...