http://www.dorneylake.com/park.htm The rowing lake is 2.2KM long and encircled by two ribbons of the shmoothest ashphalt Eton public shoolboy's parents can buy. If you're into long distance and looking for a skater-friendly place to train, look no further.
Oh, and there's a stone circle too. Didn't see it as I was busy having fun.
The side on the left of the picture is reasonably flat. It has three bridges which you can feel. This side has fewer people so if you're hammering it, you'll have more space.
The side on the right is dead flat and straight however a little busier. I took my 5 year old there on her bike. She's a bit wibbly wobbly and was all over the shop.
There are meter markers along the lake (so the rowers can pace themselves) or you could invest in a GPS thingy if you have some spare wonga.
It's a good warm up place which also happens to be on my route home from the office
There are toilets (and a shower!) in the boathouse where you can fill up with water.
The site is very open to the wind, so if it's above 15mph, try and Skog against the wind.
Remember to be nice to other lake users as this is private land and an absolute jewel.
