If you're new to town or have just never been to Emerald Lake south of Bozeman, Russ McElyea and his buddy take you on a tour (up and back) on their dirt bikes.

According to AllTrails.com:

Emerald and Heather Lakes is a 11 mile out and back trail located near Bozeman, Montana and is rated as moderate. The trail is primarily used for hiking and is accessible from July until September.

(We'd argue that "accessible" is completely weather dependent.)

It's a great hike if you have that much time, but is also great on a bike. Just remember your trail manners :-)