45 minutes due west of Bangkok is the Phra Pathom Chedi. Located in the town of Nakhon Pathom, this chedi or stupa is often claimed as the biggest in the world. Whether or not this is true might be up for some debate, as well as constitutes a stupa. Does it include pagodas? Does it include prangs? Perhaps a few other monuments that I am as of now unaware of?
Regardless, the Phra Pathom Chedi certainly is big; enough so that it has its own light atop suggesting it needs to warn off aircraft. Around the central monument is a large complex and walkway full of various temple exhibits.
Nakhon Pathom itself is a town with a lot of history, in fact it’s the oldest town of what would be considered modern Thailand. It’s the first town settled by the Dvaravati, a Mon people from Burma. They were the first to introduce Buddhism to South East Asia and spread out through the region from Nakhon Pathom. Ruins of a Dvaravati temple can still be seen only a few blocks from the Phra Pathom Chedi.
Legend has it that the original stupa was discovered overgrown and in ruins by a Thai king during his monkhood. He ordered a new, grander stupa be built in its place, culminating eventually in the Phra Pathom Chedi that can be seen today.