It is just a 1 km walk with 80 m uphill from the main road above the village Trpejca to the Krstova cave. I visited this cave during a much longer hike from Pestani to the Monastery of St Naum, and the GPS track described here is just a simplified version to reach the cave from Trpejca.
From the back of the parking above Trpejca (next to the main road from Ohrid to the Monastery of St Naum), follow a dirtroad until you reach the main road again. After 70 meters, take the dirtroad to the right and follow this for 500 uphill until you reach a more open area. When I was there, there was a small pile of stones next to the dirtroad to indicate the path to the cave. The entrance to the Krstova cave is about 40 m to the right.
Small cave 
Small cave 
Small cave
I had gotten the approximate location of the cave a few days earlier from Riste who sold tickets for the Church of St Bogorodica Zahumska (St Zaum) near Trpejca. When I was looking for the Krstova cave I came from the opposite direction of Pestani and I did not see the pile of stones at first. It took me about 1.5 hours searching in circles before I finally found a cave! When I thought I had finally found the cave and crawled into it, it turned out to be just a small cave, not more than a shallow hole!
At that time, I decided to give up on looking for the Krstova cave but after just 50 m the description Riste had given me suddenly made sense, and there was the little pile of stones indicating the path to the Kristova cave! I felt so stupid to have spent 90 minutes searching for the cave, 50 meters from its location! Stupid or not, the Krstova cave was completely worth the searching effort. It is a beautiful cave with quite a lot of decoration.
Exit of Krstova cave 
Krstova cave 
Krstova cave 
Krstova cave
After your visit to the cave, take the same way back to Trpejca. You may also want to visit the Naumova cave and Crna Pesht cave, as well as the Church and Monastery of St Bogorodica Zahumska (St Zaum).
You can view and download the GPS track here: https://www.wikiloc.com/hiking-trails/trpejca-to-krstova-cave-in-galicica-national-park-40117948
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