I've heard that folks in Berlin (like many Europeans) love a spa day, either alone or as a sort of social outing. Anyone visited a spa in Berlin that they'd recommend? I was looking at Liquidrom near Checkpoint Charlie (DJs play music as you float?!) and Vabali near Mitte. Has anyone experienced those or other spas? I'd prefer something not-too-fancy, clean but casual/low-key. Open to any recommendations!