The Grand Circuit is actually an extension of the Small Circuit and runs through Preah Khan, Preah Neak Pean to the Eastern Mebon and other temple monuments of Ta Som & Preah Rup, before returning to Angkor Wat. While it takes you a whole day long with the tuk tuk to visit the Small Circuit, a Grand Circuit tour may take three or more days. The Grand Circuit complex showcases the rich and sophisticated architecture of Khmer Empire.
Tips for Angkor Temples visit:
Some of Angkor's sites were originally built as Hindu temples, while some were built as Buddhist temples, and yet others were converted over the years. Today, most of Angkor's major temples house at least a few Buddha statues (nearly all added later) and draw a steady stream of monks and worshippers. You may be approached for donations, but you are under no obligation to pay unless you actually choose to accept incense sticks or other offerings.
Because these are still holy spaces for the Khmers (Cambodian people), it is best to follow the dress code of "long pants/skirt and covered shoulders." This is the dress code that the Khmers follow when visiting any temple or holy space.