The Wongudan, or Temple of Heaven, in Seoul, Korea. It was built in 1897, so it's relatively new in this photograph!
Joseon Korea had been an ally and tributary state of Qing China for centuries, but during the nineteenth century, Chinese power faltered. Japan, in contrast, grew ever more powerful during the second half of the century. In 1894-95, the two nations fought the First Sino-Japanese War, mostly over control of Korea.
Japan won the Sino-Japanese War, and convinced the Korean king to declare himself an emperor (thus, no longer a vassal of the Chinese). In 1897, the Joseon ruler complied, naming himself Emperor Gojong, first ruler of the Korean Empire.
As such, he was required to perform the Rites of Heaven, which had previously been carried out by the Qing emperors in Beijing. Gojong had this Temple of Heaven constructed in Seoul. It was used only until 1910, when Japan formally annexed the Korean Peninsula as a colony and deposed the Korean emperor.