Khun Dan Prakan Chon Dam

Khun Dan Prakan Chon Dam holds the world record for the largest and longest roller-compacted concrete (RCC) dam — 2,720 metres across and 93 metres tall, built from around 5.5 million cubic metres of concrete over roughly a decade before opening in 2005. It sits on the Nakhon Nayok River, about two hours’ drive from Bangkok, and holds back a reservoir used for flood control and irrigation across the province.

Walking the dam crest is free and takes 20-30 minutes end to end, with views over the reservoir on one side and the valley on the other. On weekends and public holidays a tram (around 30 THB per person) runs the length of the dam for anyone who doesn’t want to walk it in the heat; golf carts can also be rented near the entrance. For the reservoir itself, longtail boats leave from the jetty below the dam — expect to pay around 1,500 THB for a boat carrying up to seven people, or roughly 200 THB per person in a larger group, for about two hours on the water. Fishing is popular along the shoreline, and there are grassy picnic spots near the base of the dam.

Insider Tip: Go early. The dam crest has almost no shade, and by mid-morning in the hot season the concrete surface gets uncomfortably warm underfoot. Arriving by 7-9 AM also means cooler temperatures and calmer water for photos.

Watch out: Weekends bring Bangkok day-trippers and the small car park fills quickly — arrive before 9 AM or expect to park some distance from the entrance.

Khun Dan Prakan Chon Dam is often combined with a wider Nakhon Nayok loop — Namtok Sarika and the shaded gardens at Wang Takhrai both make easy add-ons on the same day. For places to stay in the area, see the Nakhon Nayok guide.