We absolutely loved our time on this tour. In Krems we only had 45 minutes but we went to both main churches and explored the alleyways and inspiring views! In Durstein we had an hour and I managed to run up the mountain to the castle ruins and had time to quickly explore town and the river after. If you're hoping to see the castle ruins but can't walk very quickly up a steep hill you won't be able to make it in time for this tour. Lastly, Melk Abbey was amazing and so beautiful. We learned a lot about its history and enjoyed our guide. The timing was very prompt. We had a nice lunch too!