Llyn Ogwen is a lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in north-west Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

. It lies alongside the A5 road between two mountain ranges of Snowdonia

Snowdonia

Snowdonia is a region in north Wales and a national park of in area. It was the first to be designated of the three National Parks in Wales, in 1951.-Name and extent:...

, the Carneddau

Carneddau

The Carneddau , are a group of mountains in Snowdonia, Wales. It includes the largest contiguous areas of high ground in Wales and England, as well as six or seven of the highest peaks in the country—the Fourteen Peaks...

 and the Glyderau

Glyderau

The Glyderau are a mountain group in Snowdonia, North Wales. The name derives from the highest peaks in the range, Glyder Fawr and Glyder Fach....

. Somewhat unusually, the county boundary at this point is drawn so that the lake itself lies in the county of Gwynedd

Gwynedd

Gwynedd is a county in north-west Wales, named after the old Kingdom of Gwynedd. Although the second biggest in terms of geographical area, it is also one of the most sparsely populated...

, but all the surrounding land (excluding the outflow) lies in Conwy County Borough.

Llyn Ogwen lies at a height of about 310 metres above sea level and has an area of 78 acres (315,655.1 m²), but is a very shallow lake, with a maximum depth of only a little over 3 metres. It is fed by a number of streams from the slopes of the mountains which surround it, which include Tryfan

Tryfan

Tryfan is a mountain in Snowdonia, Wales, forming part of the Glyderau group. It is one of the most recognisable peaks in the region, having a classic pointed shape with rugged crags. At 3,010 feet above sea level it is the fifteenth highest mountain in Wales...

 and Pen yr Ole Wen

Pen yr Ole Wen

Pen yr Ole Wen is the seventh highest mountain in Snowdonia and in Wales. It is the most southerly of the Carneddau range.The mountain lies to the north of Idwal Cottage youth hostel on the A5 road, from where it has a pyramidal appearance. It may be climbed from the hostel by a path that leads...

. The largest of these streams is Afon Lloer

Afon Lloer

Afon Lloer is a small river in Snowdonia, North Wales. It is the outflow from Ffynnon Lloer, a lake in the Carneddau mountains, and it flows into Llyn Ogwen....

, which flows from Ffynnon Lloer

Ffynnon Lloer

Ffynnon Lloer is a lake in the Carneddau range of mountains in Snowdonia, North Wales. It lies below the peaks of Pen yr Ole Wen and Carnedd Dafydd at a height of and covers an area of some ....

.

Llyn Ogwen is the source of the Afon Ogwen which flows north to reach the sea near Bangor

Bangor, Gwynedd

Bangor is a city in Gwynedd, north west Wales, and one of the smallest cities in Britain. It is a university city with a population of 13,725 at the 2001 census, not including around 10,000 students at Bangor University. Including nearby Menai Bridge on Anglesey, which does not however form part of...

. Although Ogwen is a natural lake, a dam was built in the early 20th century to raise the level of the lake in order to provide water for the use of the nearby Penrhyn Quarry

Penrhyn Quarry

The Penrhyn Slate Quarry is a slate quarry located near Bethesda in north Wales. At the end of the nineteenth century it was the world's largest slate quarry; the main pit is nearly long and deep, and it was worked by nearly 3,000 quarrymen. It has since been superseded in size by slate quarries...

. The lake is popular with anglers and is said to contain excellent trout.