Is it possible to visit the basin and wind tunnel? Is there a permanent tour or an open day? The building surely is impressive on Google maps, I'd love to visit the installations next time I'm in the US.

Absolutely not. It is a secure facility.

Thank you for your answer! I hoped there would have been a tour on selected dates or an open day like for the Capitol or some other army facilities. I'm fond of planes, boats and extravagant architecture, this facility checks all the boxes on my "wanna visit list". I'll do with the pics I can find online but I'm pretty sure I'm not the only one interested in visiting the tunnel. They should consider maybe an open day once a year for engineering enthusiasts. Or have a secure tour like Airbus and Boeing do for their respective factories and engineering plants. They also have secrets and sensitive stuff but they manage to have daily visits for the main factories and selective (advanced booking, ID required, body scan, etc.) open days for the more sensitive parts.