Trem Yr Ynys is in Betws y Coed. It's right in the middle of the village, so you can walk to everything. The house is on three floors, so there are a fair few stairs.
It sleeps eight people. Four bedrooms, two bathrooms. It's got a 5 Star rating, which means it's well-equipped and comfortable. The garden is a decent size and you can see the river from it.
There's a shop about 200 yards away, and a pub is even closer. Plenty of restaurants too, all within a couple of minutes' walk. The facilities are what you'd expect: dishwasher, washing machine, WiFi, parking. Bedding and towels are included. You can bring up to three dogs.
If you want to get out, you're right in the middle of it. You can walk or cycle straight from the door into Gwydyr Forest. For a bigger day, Snowdon is about a 30 minute drive. You can walk up or get the train from Llanberis.
Other things within half an hour: Conwy Castle and town walls are good to see. Bodnant Garden is a famous National Trust spot. Llandudno is the classic Victorian seaside town with the pier and the Great Orme.
Useful links for planning: National Trust Snowdonia and Snowdonia National Park.