'Eliza Jane', the Tunnel boring machine (TBM) broke through at the Glendoe Hydroelectric site last week, having completed eight kilometres of tunnels, and climbing over 600m in height.
The Herrenknecht TBM, owned by contractors Hochtief Glendoe JV emerged ahead of schedule on site at Scotland's first conventional large-scale hydroelectric power station for 50 years.
The new hydroelectric scheme is at Glendoe in the western end of the Monadhliath mountains, to the east of Fort Augustus in Inverness-shire.
Glendoe will be Scotland's second largest conventional hydroelectric station, and the first large-scale station to be built since 1957, when the Errochty station in Perthshire opened.
The tunnels will allow water from a new reservoir, which will be built over 600m above Loch Ness, to reach an underground power station near the south east corner of the loch before discharging into the loch.
Work continues to complete the dam, create the reservoir and build the power station which is expected to generate electricity commercially from the winter of 2008/09.
Scottish and Southern Energy, the biggest renewable energy generator in the UK, expects the plant to be operational from the end of next year.
It will have a capacity of 100MW; enough for a city the size of Glasgow at peak output.