Glendalough (/ˌɡlɛndəˈlɒx/; Irish: Gleann Dá Loch, meaning 'valley of two lakes'[2]) is a glacial valley in County Wicklow, Ireland, renowned for an Early Medieval monastic settlement founded in the 6th century by St Kevin.

Glendalough is also a recreational area for picnics, for walking along networks of maintained trails of varying difficulty, and also for rock climbing.

Kevin, a descendant of one of the ruling families in Leinster, studied as a boy under the care of three holy men: Eoghan, Lochan and Eanna.

Kevin's writings discuss his fighting "knights" at Glendalough; scholars today believe this refers to his process of self-examination and his personal temptations.

For the next six centuries, Glendalough flourished and the Irish Annals contain references to the deaths of abbots and raids on the settlement.

The destruction of the settlement by English forces in 1398 left it a ruin but it continued as a church of local importance and a place of pilgrimage.

Glendalough is on the 1598 map "A Modern Depiction of Ireland, One of the British Isles"[6] by Abraham Ortelius as "Glandalag".

Descriptions of Glendalough from the 18th and 19th centuries include references to occasions of "riotous assembly" on the feast of St. Kevin on 3 June.

The monastery in its heyday included workshops, areas for manuscript writing and copying, guest houses, an infirmary, farm buildings and dwellings for both the monks and a large lay population.

[8] See Annals of Inisfallen (AI) The Gateway to the monastic city of Glendalough is one of the most important monuments, now totally unique in Ireland.

The large mica-schist stones which can be seen up to the height of the square-headed west doorway were re-used from an earlier smaller church.

Under the southern window of the chancel, there is an ambry or wall cupboard and a piscina, a basin used for washing the sacred vessels.

[4] Almost totally reconstructed from the original stones, based on a 1779 sketch made by Beranger, the Priests' House is a small Romanesque building, with a decorative arch at the east end.

[4] This stone-roofed building originally had a nave only, with an entrance at the west end and a small round-headed window in the east gable.

The belfry with its conical cap and four small windows rises from the west end of the stone roof in the form of a miniature round tower.

The church is currently thought to commemorate St. Ciarán, the founder of Clonmacnoise, a monastic settlement that had associations with Glendalough during the 10th century.

The most recent of the Glendalough churches, St. Saviour's priory was built in the 12th century, probably at the time of St. Laurence O'Toole.

It sits on the south side of the Glenealo River, directly opposite ruins of St Ciarán’s church, beside the green road leading to the upper lake.

Only the foundations survive today and it is possible that the cell had a stone-corbelled roof, similar to the beehive huts on Skellig Michael, County Kerry.

[4] St. Kevin's Bed is a cave in the rock face about 8 metres above the level of the Upper Lake on its southerly side (with The Spinc cliffs above it).

[4] This small rectangular church on the southern shore of the Upper Lake is accessible only by boat, via a series of steps from the landing stage.

[4] Camaderry Mountain 699 metres (2,293 ft) which overlooks the upper Glendalough Lake from the north shore, contains the Luganure mineral vein which is a source of lead in the form of galena (PbS), and also contains traces of silver.

[15][16] In 1859, the Glendasan and Glendalough mines were connected with each other by a series of tunnels called adits, which are now mostly flooded, through the Camaderry mountain.

These tunnels helped drain the mineral vein and made it easier to transport ore to Glendalough where it could be more easily processed.

[23] The most notable trails used to take the steep 600–step boarded path (using railway sleepers), but replaced by a zig-zag path in 2020 from the Poolanass Waterfall up to vantage platform of The Spinc (from the Irish "An Spinc"; meaning "pointed hill"), which overlooks the upper lake and the Glendalough valley below.

[25][24][26] As the entire White Route loop is on paths (either stone/sand paths or boarded railway sleepers), it can be completed in running shoes and does not require climbing footwear; the entire 9-kilometre loop of the White Route, starting and ending at the upper lake car-park, takes circa 2–3 hours.

Glendalough's south-facing granite cliffs, situated on slopes of Camaderry above the north-western end of the valley (just above the Miner's Village), have been a rock climbing location since 1948.