Bang Pa-In is a small town situated approximately sixty kilometres north of Bangkok and about twenty kilometres south of Ayutthaya city.
Bang Pa-In's number one sight is the Bang Pa-In Palace. This palace was originally built by King Prasat Thong during the Ayutthaya Period in 1632 CE, but it was abandoned after the fall of Ayutthaya kingdom in 1767 CE. The site was partially restored by King Mongkut (King Rama IV) in the 1850's CE. The palace as it stands today, however, is mostly the work of King Chulalongkorn (King Rama V), who expanded the area into a garden filled with European-style buildings in 1872-1889. Besides these, there are also impressive Thai- and Chinese-style structures build during the same period spread around the palace compound. The palace and its grounds are maintained in immaculate shape and are well worth a visit. [IMPORTANT: As at all royal sites in Thailand, proper attires are required. "Smart casual" is a good rule-of-thumb to follow in this case.]
Across an inlet waterway adjacent to the palace is a cigar-shaped island where Wat Niwet Thammaprawat is situated. This is a Buddhist temple also built by King Chulalongkorn in 1878 CE. Most of the temple's buildings were constructed in the design of Gothic Christian churches, particularly the Phra Ubosot (the ordination hall), which has two tall spires and stained-glass windows. A simple, motorised cable-car carries visitors across the waterway from behind the visitors' parking lot to the temple and back.
Many may view that the construction of Western-style buildings, gardens and even a Buddhist temple by King Chulalongkorn was merely for his royal amusement -- BUT this is far from the truth. The King's motive here was utterly serious, wherein his kingdom's sovereignty and independence from Western colonial powers were at stake.
In hindsight, it is evident that the main agenda of the European colonial drives into Southeast Asia was to exploit the region's human and natural resources. However, the pretext used by the governments of these European countries was that they were bringing better livelihoods to those over whom they colonised -- a religion of salvation, scientific and technical know-how, improved day-to-day subsistence, education, etc.
The Thai monarchs (even as far back as the Ayutthaya kingdom) had seen through this ploy, and so had taken the stern position that Thailand and Thai culture were on par with those of the Europeans -- they can trade with us, but we would not allow them to assume dominion over our country. This is one of the primary keys to Thailand's success in being able to resist colonisation throughout the many centuries from since the first contact with Europe.
However, colonial powers became ever more forceful and hostile all across Southeast Asia in the 19th century CE. Trade and diplomatic negotiations were not sufficient to keep the colonists at bay, and more substantial measures had to be undertaken. Commissioning and constructing European-style buildings were one of these measures, i.e. on the one hand, it was a modernisation and technology-transfer process, and, on the other hand, to give tangible proofs that Thais were equally capable of managing and completing such projects. Visitors to the Grand Palace in Bangkok can also see many similarly styled builds. The most prominent of these is the Chakri Maha Prasat Throne Hall, which is a fusion of Thai and European architectural styles.
But Thailand did not get away unscathed. The country lost a significant amount of territories in the East, West and South (on several occasions literally at gunpoints) to the colonists.