Located 55km northeast of Ulaanbaatar, this popular national park is characterised by picturesque alpine scenery. It offers great opportunities for hiking, rock climbing, swimming (in icy-cold water), rafting and horse riding. For hard-core extreme-sports fanatics, there's skiing and dog-sledding in the depths of winter. The southern section caters to tourists, so it's hardly pristine (and a bit crowded with ger camps), but hikers and horse riders can easily get away from the hustle and bustle by trekking further north into the park.
Be prepared for mosquitoes, especially in late summer.
Pay the admission fee at the park entrance. Note, passengers on the public bus from Ulaanbaatar rarely have to pay this as the bus usually drives past the entrance without stopping.