This is possibly one of the best rivers I've paddled; it's a short, super high quality roadside run in North Wales. Many of the guides I have read about this river have possibly made it seem like a big undertaking with a great level of difficulty, but in low water the Aberglaslyn Gorge is actually a lot more straightforward than they suggest.
The Aberglaslyn Gorge is a short section of the Afon Glaslyn starting just south of Beddgelert. As a Grade 4 run, it obviously still has its dangers and I can only speak for the water levels in which I did it. This section of whitewater is a very intense and technical section with tight turns around rocks and some good boofs. The surrounding area is beautiful forest and crystal clear water, you could almost forget you were in Britain. It gives you a feeling of wilderness even though there is a road righ next to you on river right and a footpath on river left. You can check the level at the Glaslyn gauge for Beddgelert, usually 0.8 is a fun level.
There is a stretch of easier water above the main event (if you put on where I suggest) which is well worth it, as the main rapid will fly by in a second. Slowly the sides will begin to grow as you pass Beddgelert town. You should have plenty of time to eddy out river left and have a scout down the footpath to check out the first of the rapids. I would recommend on your first lap to eddy hop your way down, memorising the lines and getting used to the water. The river then takes a bit of a right turn, you should jump out onto the path again (river left) as the main drop is just a bit further down. There are two lines down the drop – river right of the rock in the middle skirting round the corner, this is probably where the drop is biggest – or river left of the rock, boofing off the left side of the lump in the middle (possibly easier, but also a lot of fun). Don't forget what's below the drop though! Make sure you know where you're going on them. I spent a long time just lapping this one drop by hopping out in the river left pool directly below the drop and seal launching off the big rock just above it.
We got on a lot further upstream than the guidebook suggests (on the classic Glaslyn Grade 2 section above) to make it a bit more of a trip. At the take out there is a large eddy on the river left after the road bridge, which also seems to be the place where all kit and boats float to (we found a boat floating in the eddy which was later returned to its owner). The footpath follows the river the whole way down on the river left for scouting, setting up safety, rescuing or for photographers. And you can easily do laps of the gorge by walking back up the road on river right: get out on the river right in the pool just above the rapid which goes under the road bridge at the bottom, there is then a pavement most of the way up the road, the road then gets closer to the river level further upstream and this is when you can then jump over the stone wall and get back on for another lap.
I really can't recommend this river enough!