Old Kielder Castle Cottage is on the main street in Kielder village, right across from the castle itself. It used to be a stable for the castle, built in 1775. It's semi-detached.
It sleeps four. Two bedrooms upstairs, one bathroom downstairs. It's got a 4 Star rating. There's underfloor heating on the ground floor and a wood burner in the living room. The stairs are a typical cottage staircase, so they're a bit steep.
The garden is enclosed, which is handy. It's tiered, so you get a bit of privacy. You can see the castle from it.
Being in Kielder, it's about being outside. You're right in the Northumberland National Park. The Kielder Water & Forest Park is on your doorstep. You can walk or cycle straight from the door. There's a bike store at the cottage. The local pub and the castle cafe are a couple of minutes walk away.
It's a Dark Sky Park here, so on a clear night you can see a lot of stars. The Kielder Observatory isn't far if you want to book a session. The castle has a visitor centre with a cafe and they sometimes have exhibitions.
Within about half an hour's drive you can get to bits of Hadrian's Wall, like at Housesteads. The Northumberland coast, like Seahouses, is a bit further, maybe 45 minutes to an hour. It's a good base if you don't mind driving.
Facilities: it's got a washing machine, dishwasher, WiFi, and parking on site. Bedding and towels are included. There's a cot, highchair, and a stairgate if you need them. It says up to two pets are allowed.
If you're planning trips, the Northumberland National Park and Visit Kielder sites are useful.