The old stone bridge, Spean Thma, is near the temple of Ta Keo and near the metal bridge on the road to Ta Prohm. The bridge was originally constructed in Angkorian times, but it has suffered badly through the centuries. Huge trees grow out of the stones with much of the masonry severely damaged.
Travellers who stop and look can see the corbelled arches and the remains of a stepped embankment. The Siem Reap River flows about five metres below it. The river was originally canalised by the ancient Khmers and took a straight route north to south. The river eventually cut a deep ravine and turned at right angles to the bridge, leaving it high and dry. Upriver from the bridge is a large waterwheel which has just been replaced after being removed for repairs. It's about 10 metres in diameter and an impressive sight in its own right. Yet it is ignored by most tourist groups, which focus on the ancient stones. The waterwheel is a marvellous example of industrial archaeology, and it is still used to pump water to the Takeo nurseries. Now that the rainy season is here, it is fascinating to watch the huge wheel working again.