Plans to create an iron ring sculpture at Flint Castle have been described as "insulting to Wales".
The design, said to represent the relationship between the medieval monarchies of Europe and the castles they built, was unveiled on Friday.
But critics including Plaid Cymru's North Wales AM Llyr Gruffydd said it symbolises the oppression of Welsh people.
Monuments body Cadw said the plans were "about investing in Flint".
Flint was one of the first castles to be built in Wales by Edward I - construction began in 1277.
The winning design was selected by a panel following a nation-wide competition, and the architects said it demonstrated "the unstable nature of the crown".
But Mr Gruffydd said a sculpture celebrating the conquest of Wales by Edward I was "inappropriate and insulting".
"The 'ring of steel' is the description given to the chain of castles across Wales that were built to conquer and subjugate Wales," he said.
"From a Welsh perspective, this is certainly not something to celebrate. It does not either reflect the many rich Welsh legends that could have been the source of a far more appropriate sculpture."
A petition has also been launched calling the design "extremely disrespectful". By Monday it had attracted more than 2,000 signatures.
People have also criticised the sculpture on social media.
But Andrew Barratt said: "It symbolises the role of castles, we were subjugated, it's history, sad but let's get over it living in the past won't forge our new Wales."
In response, a spokeswoman for Cadw said it recognises "that art divides opinions, encourages debate, and can be interpreted in many ways".
"These plans are about investing in Flint, increasing visitor numbers and growing the local economy. The proposed sculpture would also provide a unique opportunity to promote Welsh steel, as well as tell powerful stories that continue to shape our lives today," the spokeswoman said.
"We will continue to listen to a range of views on this important project as it evolves, and ensure that decisions over issues such as the words inscribed on the sculpture reflect local opinions and the complex and often difficult history of Wales."
A spokeswoman for Arts Council of Wales said its role was to "assist with advice in setting up the tender process and selecting the work" alongside other panellists from Visit Wales and Cadw.