Two zones, and they swap
Spa World's baths are split into a 'Europe zone' and an 'Asia zone,' each with a different set of elaborately themed pools and hot baths — Roman, Greek and Mediterranean-styled rooms on one side, Bali, Persian and other Asian-influenced designs on the other. The two zones alternate between the men's and women's sides on a monthly rotation, so which one you see depends on when you visit.
More than just bathing
Beyond the themed bathing floors, the complex includes a large pool area with waterslides that operates as mixed-gender (swimwear required, unlike the bathing floors), making it a genuine half-day option rather than a quick soak.
Practical basics
As with any Japanese bathhouse, the themed bathing floors themselves are visited without swimwear and follow standard sento etiquette — wash thoroughly before entering any bath, and check the venue's current tattoo policy in advance if that applies to you.