Called sekimori-ishi (barrier-keeper stone), the rope tied stone has several meanings: that the tea house is occupied and the tea ceremony is underway, or that if you go further up the alley you may intrude. Sometimes, the sekimori-ishi also has a spiritual meaning, marking the entrance to a spiritual space...
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 10mm
Aperture: F/5.6
Shutter Speed: 1/200s
ISO Sensitivity: ISO 320