Not too distant north of Bangkok is Ayuthaya, capital of Siam from 1350 until conquered by the Burmese in 1767. This is a mostly-restored set of ruins on a large garden-like set of grounds, I believe Wat Chai Mongkhon. This is one of several locations of great beauty and serenity in Authaya. There is still a functioning temple used for daily worship as well as many stupas, Buddha images, courtyards and garden areas for a picnic or just to meditate.