Bovska skaklya waterfall (named after Bov village and Skaklya river) is located in the middle of the beautiful Vazova ecotrail (named after one of the most famous Bulgarian writers - Ivan Vazov, who was deeply inspired by this region) in Iskar gorge. The ecotrail is only one hour away from Sofia (by train and car) and it takes only one hour to walk along it (and of course, one more hour to go back) - I think it is my favourite one-day trip close to Sofia!
You can start the ecotrail from either Gara Bov village (down at the river on the main road that connect Sofia and North Bulgaria) or from Zasele village (on top of the hill where the waterfall falls). If you travel by car, I recommend you start from Zasele village. On the way to Zasele village there is a viewpoint where you can take scenic photos of the gorge and the river below you. From Zasele village you go down the hill and you will reach the waterfall in 30 minutes. Then you can either go back or go to the very beginning of the ecotrail close to Gara Bov village (which will take you 30 minutes more). At the end you can simply go back to Zasele village where you left your car.
If you travel by train, you should stop at Bov railway station, cross the railway and a bridge and turn right (direction North). In about 50 meters, you will see a sign "Ivan Vazov ecotrail" (in Bulgarian: ВАЗОВА ЕКОПЪТЕКА) and you should turn left. In about a kilometer and a half you will reach the start of the ecotrail. Don't worry - the GPS can also take you there, on Google maps it is marked as "Vazova trail".
I personally travelled by train, so I started the "hike" (because you go from the river up the hill) from the railway station. At the start of the ecotrail ("Vazova trail" as marked on the GPS) you need about 30 minutes to reach the waterfall. You will be able to see it from far away though - the waterfall has three levels, so it is very scenic! Once you reach the waterfall, you can either cross it and continue the hike for about 30 minutes more (to reach Zasele village) or go back. I personally continued the hike, went up the hill to Zasele village and I definitely recommend this option! At Zasele village there are a couple of view points towards Iskar gorge as well as benches where you can enjoy your lunch. Afterwards, I simply went back the same way and got the train back to Sofia (it took me an hour to go back from Zasele village to Bov railway station).