I was there for 3 days and it was one of the most amazing holidays I've had. The Temples of Angkor just awe you with the intricacies and the forethought in its architecture, you simply cannot believe the civilization was so advanced for that period of time. A day pass costs USD20 and gives you access to the whole park but if you think you can walk it, think again. Main mode of transportation are the tuk-tuks which charge based on if you take the big tour, which covers the entire Angkor complex, or the small tour which mainly covers the most famous temples like Bakheng, Ta Prohm and Angkor. If you plan on doing the big tour, which covers more or less 21 temples, I suggest taking the 3 day pass as this way you do not have to rush and get to enjoy the temples more. It gets only 4 stars though because I guess the management cannot cope with the amount of people visiting there and many of the sites are/have crumbling/crumbled largely due to tourism.