This waterfall trail is quite popular with Western Cape locals and since the area is a UNESCO World Heritage Site it's not really a hidden gem anymore. Nonetheless, the scenery is stunning, so I recommend you go, especially because you can swim in the rock pool on the route, see different kinds of birds and enjoy a scenery that is quite different from the Cape Town area.
The route is generally rated as moderate and since you will be hiking around 3 hours, make sure to bring enough water with you. Also note that this area is infamous for rapidly changing weather conditions, so make sure to be prepared accordingly and always check the weather report.
To save the environment and delicate flora and fauna, only a limited number of people are allowed to enter Jonkershoek per day. You must purchase a permit at the gate for 60 ZAR (only card and contactless!!) and be out of the park by 6 PM. If you want to make sure that you can enter the reserve and the maximum amount of people hasn't entered already before you get there, you can buy your permit online: https://www.mtotrails.com/permits/jonkershoek/1.
Specifications:
Distance: 9.8 kilometers
Difficulty: moderate
Height difference: 336 meters
Link to hike: https://www.alltrails.com/de/route/south-africa/western-cape/jonkershoek-waterfalls-day-hiking-trail?u=m&sh=cpwn1g