Damien “World’s Richest Living Artist” Hirst is expanding his historic home facing London’s tony Regent’s Park, though you won’t notice much of a change at street level. That’s because the spot-master is building the enormous complex underneath his half-acre garden. Once completed, it will include a sauna, a steam room, a two-story-tall “art room,” a cargo elevator capable of lifting large-scale artworks weighing up to 11 tons, and an 82-foot-long swimming pool — that’s almost long enough to accommodate five of his pickled shark sculptures end-to-end.

The 14-bedroom house, located at 20 Hanover Terrace, is part of a villa commissioned by the Prince Regent in 1811. It was designed by architect John Nash (who designed Buckingham Palace, Piccadilly Circus, and many other historical sites throughout the UK) and completed in 1832. It is listed as a Grade I building by Historic England, meaning it is “of exceptional interest.” Hirst bought it in 2014 for £39.5 million (~$57.9 million) and in October of last year filed plans with the City of Westminster to vastly expand its below-ground footprint. The plans were quickly approved despite objections from officers of Westminster City Council over the number of trees that would have to be felled — 17, according to an official tree report. Last month, Hirst filed an amended version of the plans that indicated a lower basement level than the original scheme, earning a terse rebuke from the city council.

“We do understand that the previous approval limits the ability of Westminster City Council to reject what amounts to amendments of that scheme but, it is in their responsibility to preserve Listed Buildings, to maintain Conservation Areas and, to ensure that the development does not have a substantial detrimental effect on the neighboring properties,” a letter of objection filed with the City of Westminster reads. “In this instance, that balance has already tipped in favor of the development and any further proposals should be rejected, based on Westminster’s own policy guidelines.”

Despite the dissenting city counselors, Hirst’s subterranean splash zone is set for construction. Blueprints for the complex, by British architecture firm Purcell, show a vast underground space connected to the historic Nash building by a staircase and interior elevator, and to the garden by a staircase in an adjacent utilities building and a cargo lift tucked behind the garage (which is also equipped with a lift for stacking cars, naturally). It all sounds very reminiscent of another famous rich white guy’s underground lair.

Yes, that other enigmatic billionaire, Bruce Wayne, built a similarly large series of subterranean laboratories, storage spaces, and exercise facilities underneath his own historic home, Wayne Mansion. That underground studio, dubbed the “Batcave,” was where he developed his durational performance art project “Batman,” a relational aesthetics piece that sought to expose the latent vigilantism of extremely rich men living under late capitalism. Perhaps Hirst is hatching a superhero performance of his own.