Best Cairngorm hikes?

Around Loch an Eilein is a pleasant route but would be considered an easy walk of about 3.5 miles.

For something more challenging, head to the Cairngorm Cafe at the southern side of the Glenmore Nature Reserve. There is a route to the south that goes between Creag an Leth Choin and Cairn Lochan before turning east towards the latter. It then progresses to Stob Coire an t-Sneachda then to Cairn Gorm. It then turns north to the start point. Probably 8 miles and 5 hours. It is referred to as the Northern Corries circular in some books.

If you are comfortable with a map and used to walking then you have lots of options and most are fine for self guiding.

The Walk highland web site is the walker's Bible.... Have a look at ideas for walks from Aviemore, Rothiemurchus and the Northern Cairngorms here. Information and map for Loch an Eilein here. Information and map for the Northern Corries here (read the cautionary advice for it).