My Son Sanctuary is like a mini version of Angkor Wat. It is located about 40km from Hoi An and takes around 1 1/2hrs to get there by bus. The easiest way to visit would be to join a day tour - which could also include a side trip to a nearby island off Hoi An.
The temple itself is in ruins and not yet fully restored. Actually I hope they would leave it this way as ancient monuments that are restored often lose their mystical aura. There are only a few structures which are relatively intact - but even from these you could visualize the grandeur of the temple in its glory days. Those who have visited Angkor Wat would no doubt find this underwhelming - but it is still an amazing site - to see the ingenuity of our ancestors thousands of years ago.
My Son was built by the Cham people of central Vietnam who also fell under the influence of Hinduism and Buddhism like their surrounding neighbours in Cambodia and Laos. I always wonder how the designs are transmitted from India to South-East Asia without the convenience of drawings. The artisans must have carried the designs in their heads and travel across thousands of miles to build these amazing structures.