Gorilla and chimpanzee trekking in is a rare and humbling experience. A chance to see these rare and dignified creatures in their natural habitat may be a once in a lifetime opportunity. Do see Rwanda and Tanzania for more details. Staying in remote but lovely lodges you will need to make sure you book well in advance to secure one of the limited licences available to do this.
You will need to have a relative level of fitness as the terrain can be challenging as can the humidity, but once there and having experienced the interaction between these family groups, any challenges will pale into insignificance,