Detailed study of Tiwanaku began on a small scale in the mid-nineteenth century. In the 1860s, Ephraim George Squier visited the ruins and later published maps and sketches completed during his visit. German geologist Alphons Stübel spent nine days in Tiwanaku in 1876, creating a map of the site based on careful measurements. He also made sketches and created paper impressions of carvings and other architectural features. A book containing major photographic documentation was published in 1892 by engineer Georg von Grumbkow, With commentary by archaeologist Max Uhle, this was the first in-depth scientific account of the ruins.