"We are extremely happy," the architect behind the project, Carlos Quevedo, told The Local on Wednesday. "For us it's an enormous recognition of a job that took five years and a huge effort."
El Castillo de Matrera, in Cádiz, southern Spain was constructed in the ninth century and has been a National Monument since 1949.
But a recent restoration of the privately-owned castle had locals and historians up in arms about what many of them classed as a "botch job", which resembled more a 1960s multistorey car park than an ancient Moorish castle.
"They used builders instead of restorers, they've wrecked it," one local told Spanish TV channel La Sexta.
"The consolidation and restoration (so-called by the project's architects)… is absolutely terrible," the organisation Hispanianostra, which campaigns to preserve Spain's cultural heritage, wrote on its website.
"No words are needed, you just need to look at the photographs," it added.
It has become infamous as the biggest bungled repair job in Spain since an elderly lady attempted to restore a fresco of Christ with disastrous results.
But to the surprise of many of its critics, the castle was nominated for a prestigious global architecture award, the Architizer A+ in the architecture and preservation category.
The winners were announced on Tuesday, with the castle scooping the popular vote, a prize Quevedo will go to collect at the awards ceremony in New York on May 12th, the architect told The Local.
"Just being a finalist was already a huge recognition of our hard work but we are delighted to have won the prize," Quevedo told The Local.