Apparently that's not a totally bizarre concept, with Polish architect Krysztof Kotala of 8 + 8 Concept Studio releasing detailed plans for an underwater court complex, which she envisions off the coast of Dubai - between the Burj al Arab and Palm Jumeirah islands in the Persian Gulf, to be exact.
Her plans include turning the rooftop of the imagined seven-court complex into a flourishing coral reef, attracting sea life to the structure and effectively creating a manmade atoll.
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It sounds crazy, but apparently it isn't completely implausible - Kotala studied at London's Royal Institute of British Architects as well as Poland's Krakow Polytechnic and Germany's Münster University of Applied Sciences, so she knows her stuff. If it ever goes ahead, the aquarium/tennis court complex would be a modern engineering feat, requiring a single sheet of (presumably extremely heavy duty) glass large enough to cover the entire area. We just wish they'd thought of this when they designed Sydney's Harbour Tunnel.