They're in Ocho Rios and they're the most famous falls of Jamaica. The falls are really spectacular and it is possible to climb them.
The place is often crowded because of the cruise ships coming to Ocho Rios. Sometimes it is even too crowded and it is better to visit the falls in the afternoon after the organized tours have left.
You can rent shoes not to slip in the falls and they provide you tour guides. The falls are in wide park rich of vegetation and there is also a craft market selling the typical tams, carvings, wrapping and so on. There is an entrance fee which includes the guides to climb the falls. Dunn's River Falls close at 5pm.