A controversial restoration of an ancient Spanish castle has been awarded an international architecture prize, despite being lambasted by a national heritage group as “lamentable”.

Spanish studio Carquero Arquitectura’s modernist reinterpretation and renovation of Matrera Castle was the Popular Choice winner at the Architizer A+ Awards, which promotes and celebrates “meaningful architecture”.

The 1,000 year-old stricture, which was falling into ruin, was propped up by a white cuboid structure, formed of some of the original limestone, and restored to its original dimensions.

According to the studio: “The medieval towers that are distributed on our national territory represent a perfect harmony of natural and artificial landscapes from an architectural, cultural and iconic perspective. We approached the work in recognition of the memory of the castle’s physical consistency and aesthetic and historical polarity in order to transmit to the future.

“The renovation aimed to avoid the aesthetic mimicry that involves falsification or loss of value of authenticity. The historical value is enhanced.”

In response to the work, heritage group Hispania Nostra said: “It is indeed lamentable, surprising and very bad. No words are needed, you just need to look at the photographs.”

Speaking to the Guardian after hearing of the award win, defiant project architect Carlos Quevedo said: “People have different aesthetic opinions. We were sure of the work we did. The critics didn’t like the change to the monument. Many have been negative, but architects – not only from Spain, but internationally – have sent me messages saying the project is good.”

A number of leisure architecture projects won Architizer A+ Popular Choice prizes (PCP), as well as awards from the 300-strong jury of international architects and developers – which included Bjarke Ingels, Rem Koolhaas, Nathalie de Vries, James Corner, Jeanne Gang and Sou Fujimoto.

Among the successful projects previously covered by CLAD are Zaha Hadid’s Messner Mountain Museum Corones (Museum, PCP); Volker Giencke’s Great Amber Concert Hall (Theatre, PCP); MIA Design Studio's Naman Pure Spa (Healthcare and Wellness, PCP and Jury); New Wave Architecture Polour Rock Gym (Unbuilt Sports & Recreation, PCP and Jury); and Wolfgang Buttress’ Hive (Pavilion, PCP and Jury).