Boho Caves form an extensive underground network of passages created by the chemical weathering of joints (strongly directional natural fractures) in the very pure Dartry Limestone. An account of the entire complex is given in the site record ‘Belmore, Ballintempo & Tullybrack Uplands; Boho' which explains the relationship between the main sink (the entry point of most of the water into the system) and the rest of the system. The water source is the Aghanaglack River and about 100m upstream from the main road junction in Boho village is the sink where the main flow enters the caves when the river is in spate. Water entering here flows either into the Main Stream Passage or the Sewerage System, both prominent passages.
In times of exceptional rainfall the river flow exceeds the capacity of the sink and continues into the adjacent field where it sinks into a number of shake holes that feed into a series of passages called the South Series, south of the Quarry Entrance.
