Baron Empain lived in a fantastical and highly eccentric Hindu temple–inspired mansion, with the facade bedecked with elephants and serpents. Unfortunately it has been closed to the public since 1997 when ‘Satanists’ were allegedly holding rituals here; it turned out they were a bunch of upper-class teenage metalheads. Good news, though, is on the horizon. Restoration work has began on this architectural oddity, and it's planned to become a cultural centre, with the finishing date pegged for late 2019.
Until then, it's not worth a dedicated trip, but keep an eye out for it on your way to and from the airport.
The palace is due east from Heliopolis Basilica, at the end of Sharia Nazih Khalifa.