[en] This report describes the lithology and geological structures of the ONKALO underground rock characterization facility access tunnel in chainage 1980-3116. This part of the tunnel was excavated and mapped from spring 2007 to autumn 2008. The bedrock is very heterogeneous and mainly composed of veined gneiss and diatexitic gneiss, but many felsic dykes and sections of pegmatitic granite also occur. In addition, small sections of mica gneiss and K-feldspar porphyry are present. There are also numerous inclusions of mica gneiss, quartz gneiss and skarn. The foliation dips moderately towards SE. 14 fold axes and axial planes were measured from the ONKALO tunnel in chainage 1980-3116 and all have been interpreted to belong to deformation phase D₃. The measured fold axes have various orientations, but most have moderate plunges and ENE- or WSW-trending ones dominate. The axial planes typically dip moderately towards SE. An almost vertical lineation was also measured from mica gneiss on two locations. A total of 7668 fractures were measured. Three main fracture sets were distinguished from the measured orientations: set 1 fractures are vertical and strike approximately NS, set 2 fractures are more or less horizontal and set 3 fractures are vertical and ENEWSW- striking. The most common filling minerals are calcite, pyrite, chlorite, kaolinite, epidote, muscovite, quartz, biotite, and illite. Of the measured fractures, 579 were slickensided. The slickensided fractures are mainly either sub-vertical N-S-trending (set 1) or sub-vertical NE-SW-trending, with dip to SE. Slickenside surfaces show N-S- and NE-SW-trending lineations, with shallow dip. The slickensided fractures are mostly strike-slip faults with both sinistral and dextral sense of movement. The chainage 1980- 3116 contains 170 tunnel-crosscutting fractures. The orientation is mostly vertical N-Sstriking, sub-horizontal or vertical E-W- trending. 27 deformation zone intersections were also observed, 23 brittle deformation zones and 4 high-grade ductile zones. Q-classification was used in order to determine the rock mass quality for every ∼ 5 m long section of the tunnel. The Q-quality varies from very poor to exceptionally good, being mainly extremely good. The exceptionally good rock quality is concentrated to the first 500 m of the studied section; this is mostly due to the change in SRF value from 1 to 5 after chainage 2500. At brittle fault zone intersections, the rock quality varies typically from very poor to good. (orig.)