Christine Whitehouse was with her husband and two family friends when she fell at the Dam of Arade, Silves in the Algarve.
A cover over the 10 ft well opened beneath her.
Despite emergency crews arriving 30 minutes later and attempts to resusciatate her, she died from multiple injuries at the scene.
At an inquest at Cannock Coroners' Court, her husband Anthony Whitehouse described hearing a 'clang' and turning round to see his 60-year-old wife disappear down the well.
He said: "I saw the top of my wife's head disappearing down the hole and the cover opening up.
"Her eyes were closed and she didn't make a sound.
"I have been back to the site numerous times, they are heavy covers, it just doesn't make any sense at all."
Mr Whitehouse said his wife had been taking pictures at the dam seconds before the tragedy, passing through a gateway to get a better view.
He said: "Our friends took us sightseeing to the reservoir.
"We did pass metal gates that were locked but that was to stop vehicle access. There was a large gap to pass through but it has now been blocked. There were no signs on the gate prohibiting access.
"We went past to see the view and the dam equipment. Christine was taking photographs, like she always did. She was stood to the side of the concrete."
Following her death the family returned to the spot where she died five days later on June 17, which would have been her 61st birthday.
During the visit her son spotted a pipe on the other side of the well cover to where Mrs Whitehouse was standing before she fell.
Mr Whitehouse said: "My son pointed to the pole and said, 'that's what killed mum'.
"The size of the pipe matched the bruise on her head. She fell forward and must of hit her head and fell down the hole."
No further action was taken by Portuguese police and her funeral was held at St Thomas Church in Walton on June 27.
The inquest took place after translated police documents were sent to the court.
Mr Haigh, senior coroner for Staffordshire South said the 'exact sequence' of events were difficult to confirm but concluded it was a 'genuine tragic accident'.
He recorded his verdict as an accidental death.