The Isabel Zendal complex, which covers 80,000 square metres (860,000 square feet) cost nearly €100 million ($120 million).
Its purpose is to ease pressure on hospitals in the Madrid region, which has suffered one of the most deadly outbreaks of the novel coronavirus.
Isabel Diaz Ayuso, the conservative leader of Madrid's regional government who kicked off the project, attended the opening of the vast complex near Barajas airport on the city's eastern flanks.
Wires could be seen dangling from the ceiling of the still-empty hospital, with the first patients expected to arrive next week.
So far, the region has recruited 116 medical staff to work there, but has not said whether it intends to contract more.
The hospital “is adapted to suit any situation we might go through” said Diaz Ayuso, indicating its intensive care unit would be “the most advanced in Madrid”.
Los españoles tenemos desde hoy el Hospital Enfermera Isabel Zendal, que será referente en la lucha contra el virus en Madrid.
Con la tecnología más avanzada servirá en catástrofes, epidemias, listas de espera… Descongestionar hospitales. pic.twitter.com/vlSd0me2TS
— Isabel Díaz Ayuso (@IdiazAyuso) December 1, 2020
Set to open in stages, Isabel Zendal will be mainly used to reduce pressure on other hospitals so they can gradually recover non-Covid-19 activity, from waiting lists to surgeries and medical care consultations, the region said last week.
But the hospital's construction has sparked opposition, with dozens of healthcare professionals demonstrating outside the new building to criticise a project they say is “useless” at a cost that came in twice the initial budget.
“They're inaugurating a hospital which we see as unnecessary. There are unused beds in other hospitals,” said Olga Álvarez, a lab technician at the city's Gregorio Marañon hospital and member of the MATS health workers union.
The money used to build Isabel Zendal could have been funnelled into resources that were “really necessary like contact tracers, personnel or material,” she added.
“A public hospital can't be bad news for anyone, except for those with a political agenda,” remarked Diaz Ayuso, pointedly referring to the absence from the opening of Salvador Illa, health minister in Spain's leftwing government.
The Madrid region's hospitals were overwhelmed during the first wave, prompting the military to set up a vast field hospital in an exhibition centre to cope with soaring patient numbers.
Spain has been badly hit by the pandemic, so far counting more than 1.6 million cases and losing over 45,000 lives.
Of those figures, one in four deaths occurred in the Madrid region as well as just over a fifth of all infections.