Trieste and its surroundings offer some interesting sights, which can be visited during the 5-day round trip:

• At the end of Stage 1 or before the start of Stage 2: The Rilkeweg between Sistiana and Duino Castle is a walkway about 3 km long, named after the German poet Rainer Maria Rilke, author of the Duino Elegies written at Dunio Castle).
• At Stage 3: The Grotta Gigante - the largest cave in the world open to visitors, with a 100-meter-high hall (interior view on Google maps: https://goo.gl/maps/fpQ1aFdBRbt)
• At Stage 4: The Lipica Stud Farm in Slovenia is the namesake for the white Lipizzaner horses and offers an extensive program for visitors, including horseback riding demonstrations. However, if you plan to visit here, you should bring a little more time and shorten stage 4 (e.g. by spending the night in the Hotel Maestoso directly at the stud farm)
• At Stage 5 we automatically walk through the nature reserve Riserva Naturale della Val Rosandra

We recommend, after the round trip, to spend a few days in Trieste itself.