Ayutthaya or Kanchanaburi?

Neither town is anywhere near the sea, and both leave sand and salt water to another stop on the route. Kanchanaburi does at least offer fresh water to swim in: the turquoise pools of Erawan, and a float on the River Kwai beside a raft house.

In Ayutthaya the three rivers are busy working waterways, so swimming means the hotel pool and nothing else.

Both serve cheap, honest provincial Thai cooking with little fine dining, but Ayutthaya has a slightly stronger local identity. Its boat noodles, grilled giant river prawns and roti sai mai sweets are dishes people seek out by name.

Kanchanaburi's strength is the setting rather than any speciality: river fish such as snakehead eaten on floating restaurants at sunset, plus a backpacker strip that does Western breakfasts.

Ayutthaya has a whole lost capital to explore, and Kanchanaburi tells one wartime story. Ayutthaya ruled Siam until 1767, and its ruins fill the island: the three chedis of Wat Phra Si Sanphet, the Buddha head held in tree roots at Wat Mahathat, the crypt of Wat Ratchaburana, and the old Portuguese and Japanese quarters to the south. You can spend several days here and still find more.

Kanchanaburi's sightseeing centres on the Death Railway: the bridge, the war cemeteries, the Thailand-Burma Railway Centre and the JEATH museum. It is moving and well explained, but apart from a few cave temples there is little old architecture, and one full day covers it.

Kanchanaburi has a bit more going on after dark. A riverside bar strip has pool tables and the odd cover band, and at weekends karaoke and party rafts drift noisily down the river, though there are still no clubs.

Ayutthaya is quieter still: a handful of backpacker bars and riverside terraces facing the floodlit temples, and most people are in bed before midnight.

Kanchanaburi sits where the plain meets the forested limestone hills along the Burmese border, and that gives it real wild country. There is the seven-tier trail at Erawan, the falls and caves of Sai Yok, the Lawa cave, and reservoirs for kayaking and long-tail trips.

Ayutthaya offers only the gentle side of the countryside: rice fields, canals, egrets over the paddies and a boat around the island at dusk. For forest and waterfalls you have to go two hours to Khao Yai.

Ayutthaya's position makes day trips easier. Bangkok is about an hour and a half away by train, the Bang Pa-In summer palace is twenty minutes off, and Lopburi's Khmer temples and macaques are an easy rail trip north.

Kanchanaburi's best outings follow the railway up to Nam Tok and Hellfire Pass, with the Khmer ruins of Prasat Muang Singh and the canal markets to the east. Distances are longer, though, Bangkok makes a tiring day, and the border towns really need an overnight stay.

Kanchanaburi gives children more to do with their hands and feet: swimming at Erawan, the slow train, raft-house nights and an open safari park. The war cemeteries and museums will mean little to young children, though, and nearly every outing needs a minivan.

Ayutthaya's ruins impress for a morning, but climbing is mostly not allowed, shade is scarce and nothing is designed for children. A tuk-tuk circuit or boat ride is the usual way to keep the day short.

Ayutthaya is a little easier to manage. Its main ruins sit on an island a few kilometres across, flat enough to cycle on quiet back lanes, with tuk-tuks for hire and small ferries over the rivers.

Kanchanaburi's town is strung out along the river, and its best sights lie an hour or more outside it, served by sparse buses and a slow train. Most visitors end up renting a scooter, hiring a driver or joining a tour.

Neither town is a reason to shop, and both come down to night markets and temple-gate souvenirs. Ayutthaya has the woven goods of the royal crafts centre at Bang Sai downriver, while Kanchanaburi's one speciality is blue sapphire from the province's old mines, which takes real knowledge to buy well.

Both are among the cheapest stays in Thailand, with guesthouses, market food and transport costing very little. The extras differ. In Ayutthaya they are the separate entry fees at each ruin and a tuk-tuk circuit, while in Kanchanaburi the bigger costs are national park fees, private drivers and the upstream river resorts.

Performance life is close to absent in both, and each has one set-piece event built around its history. In Ayutthaya, the World Heritage fair stages light-and-sound shows and classical dance among the ruins. Kanchanaburi's River Kwai Bridge Week re-enacts the wartime bombing of the bridge with fireworks.

Kanchanaburi is the better place to switch off. Raft houses and resorts on the upper River Kwai, with hammocks over the water and jungle on the far bank, are made for idleness, and some have proper spas. The small hot springs at Hin Dat add a soak on the way into the hills.

Ayutthaya keeps to cheap shophouse Thai massage, and its rest comes in the late afternoon, when the tour buses leave and the riverside terraces go quiet.