During the mid-18th century, the Sultanate of Yogyakarta began work on Taman Sari Water Castle. Comprised of lavish gardens and pools, Taman Sari also featured a bizarre man-made sea, connected beneath the ground with underwater tunnels and small island buildings. One of these island structures was used as a mosque, and was only accessible by underwater passage.

The tiny mosque was only one story, and although basic, had all the necessary parts of a mosque including a mihrab, or small niche guiding worshippers toward Mecca. It also featured a series of staircases leading from the underwater entrances resembling MC Escher’s relativity. Staircases lead up from five different doorways to a central platform and another staircase connects the five lower staircases to a higher doorway.

Brimming with mystery, the plain mosque is only one of the wonders of the entire Taman Sari Water Castle complex. Today, many of the remains of the great 17th century compound have been lost. Pools have been filled in, which allowed for the discovery of many of the underground structures, but have destroyed the pristine castle quality. Human settlements have taken the place of the man-made lake, and much of the other buildings left standing are worse for wear. In 1995, the entire complex was listed as a tentative World Heritage Site.