Paul Howard and his daughter were digging out a fish pond when they began finding bones and bits of pottery.
Startled, they carried on excavating and hit what they first thought was rubble, their spades knocking against whole flints amid the roots of an ivy tree they had just pulled up.
Following the stones round more carefully they discovered what looked like a Roman or medieval well, and there was more inside.
Mr Howard, of West Avenue, Ormesby St Margaret, began digging a few feet inside the circle - his careful scooping revealing a new item to examine at every stroke.
After a while the pair had unearthed dozens of bits of bone, shells, shards of pottery, nails, a fish hook and even a glinting buckle - tantalising glimpses of a world gone by.
The 52-year-old artist and his wife Michelle, 53, said it had been a fascinating process that had fired their daughter Ruby's imagination.
He said he had turned amateur archaeologist to get to the bottom of the mystery, that deepened at every turn.
"When I started doing it, it was hard work," he said. "But when we starting finding things it really speeded us up.
"We started to find some bones and big stones but as we moved across we realised it was going round and round.
"I went down a bit and could tell it was quite nicely built.
"It has created a lot of interest and has made us think about history and what was here before.
"We did wonder if we should call the police initially but the bones seemed too short and stubby to be human."
He said their 1930's built house had its own modern well, now filled in, but that their discovery appeared to be altogether more ancient, possibly Roman given the size of the bricks, they had been told.
What was found inside, possibly tossed in centuries ago, seemed like everyday food stuff, the bones showing signs of being cut and split for the marrow inside.
Mrs Howard, an occupational therapist, said it would be nice to get an expert opinion on what they had dug up.
The family is poised to take the finds to Gressenhall over the summer in the hope historians there can tell them more, but getting someone to look at the well in real life was proving more difficult.
Adding to the intrigue was a dig some years ago in neighbouring Firs Avenue, said to the be the site of grand manor house.
Can you help the family in their quest to find out more? Email liz.coates@archant.co.uk
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