In the vicinity of Honpoji Temple, just east of Horikawadori, one finds the establishments of the Three Sen Houses of Tea. Although none of these is open to the public, they have imposing entrance gates and in the neighborhood one finds several shops selling tea utensils.
When in 1591 Sen Rikyu was killed by Hideyoshi, his heirs dispersed to seek refuge in the provinces. Hideyoshi was however persuaded by his generals to restore the house of Sen Rikyu and the choice fell on son-in-law Sen Shoan (1546-1614), who was allowed to establish himself as teamaster in the Fushinan teahouse of Sen Rikyu.
Next in line came Shoan's son and Rikyu's grandson Sen Sotan (1576-1658), who strongly emphasized the simplicity of the tea ceremony in his way of life and choice of tea implements.
Sen Sotan had four sons and here is where the tradition splits. His two elder sons opted for other professions than tea, so the tradition was inherited by the third son, Sen Sosa (1619-1643). When the youngest son, Sen Soshitsu (1622-1677) became twenty years of age, Sen Sotan retired to the back of his property. He continued to be active in tea and in fact developed a new tradition, the "tradition of his later years," which he transmitted to his youngest son, Soshitsu. As they were living at the rear of the Sen household, it became known as Urasenke, "ura" meaning "rear," and "senke" "Sen household." The original tradition continued by Sosa was from then on called Omoteseke, "omote" meaning "front" as Sosa was living in the front part of the property.
The second son, Sen Soshu (1593-1675), later returned to live in family property on nearby Mushanokoji street and the tradition he developed was called Mushanokojisenke, making it the third Sen House.
To sum up:
Omotesenke - est. by Koo Sosa - representative teahouse: Fushinan (the original teahouse of Sen Rikyu); current Iemoto 14th generation Sosa, teaname Jimyosai.
Urasenke - est. by Senso Soshitsu - served the Maeda clan of Kaga (Kanazawa) - representative teahouse: the one-and-three-quarter mat Konnichian; current Iemoto Sen Soshitsu XVI (born 1956), teaname Zabosai.
Mushanokojisenke - est. by Ichio Soshu - Soshu served the Matsudaira daimyo of Takamatsu - representative teahouse: Kankyuan; current Iemoto 14th generation Soshu, teaname Futetsusai.
As is often the case with Japanese traditions split along family lines, differences between the three Senke are minimal. Apparently the Omotesenke whisk the tea more than the Urasenke, creating more foam in the powdered green tea. Mushanokojisenke is the least known of the three, also in Japan, but especially abroad - it is the only one without an English webpage.
Urasenke is by far the most active outside of Japan (for example via the International Cha Culture Foundation), but also engages in tea promotion in Japan itself, for example by opening its tea library Konnichian Library to the general public, by the exhibitions it organizes in the Chado Research Center Gallery, and via its publishing house, Tankosha.