Wat Pho is behind the Grand Palace and it is well worth the visit.
We couldn't get into the Grand Palace because they have a strict dress code. Make sure your legs an arms are covered. If you're wearing a dress take a sarong or two to cover up with. They do have clothes you can borrow but the line is incredibly long. That is why we didn't go in, the expected waiting time was an hour.
Wat Pho is a must. It was founded in 1781 AD. It is famous for being one of the oldest Wats in Bangkok and it has the largest reclining Buddha in Thailand.
The reclining Buddha is 15 m high and 43 m long with his right arm supporting the head with tight curls on two box-pillows of blue, richly encrusted with glass mosaics. It is so beautiful.