Istanbul or Kas?

For swimming, Kas is clearly the better place. People swim from wooden decks and rock platforms straight into very clear, deep blue water, and there are two small pebble beaches by the harbour. For sand, the bright cove at Kaputas and the long dune-backed strand at Patara are both a short ride away, and boats stop at coves no road reaches.

Istanbul sits on the water but is not a beach city. The sea near the centre is for looking at, not bathing in. The sandy beaches at Kilyos and Sile are about an hour north and known for strong undertow, and the Princes' Islands coves only make a pleasant half day.

Istanbul is one of the reasons to travel in Turkey at all. The whole country's cooking comes together there, from Black Sea anchovies and south-eastern kebabs to Ottoman palace dishes. You can graze through Kadikoy's market streets, eat lunch at a lokanta with the day's stews, and spend long meyhane evenings over meze and rakı.

Kas cooks well for a small town, with good village breakfasts, herbs from the Lycian hills and grilled fish by the harbour. But a few streets serve much the same menu, so after a few days you will have seen most of it.

There is very little contest here. Istanbul was an imperial capital for many centuries, and the historic peninsula alone holds Hagia Sophia, the Blue Mosque, Topkapi Palace and the Basilica Cistern. Beyond them are the Süleymaniye, the Chora mosaics, the Theodosian walls and the Bosphorus palaces.

In Kas the past is part of the walk rather than the reason to come. A small Hellenistic theatre faces the sea, the Lion Tomb stands at the top of the shopping lane and rock tombs are cut into the cliff, all seen in a morning. The great Lycian cities have to be reached by road.

Istanbul has a real night out. The side streets off Istiklal Avenue are full of small bars and meyhanes that end in singing, and Kadikoy and Moda are younger and cheaper. In summer the Bosphorus clubs at Ortakoy and Kurucesme stay open until dawn.

In Kas the night is a late dinner followed by a drink on a terrace or in a music bar behind the harbour. A few places stay busy past midnight in high summer, there are no clubs, and the town goes quiet early outside the warm months.

Kas is the place for the outdoors. Limestone mountains drop straight into some of the clearest water in the Mediterranean, and there are reefs, caves and wrecks to dive a short boat ride out. Day sections of the Lycian Way follow the cliffs, paragliders launch from the mountain above town, and you can wade up the cold Saklikent gorge.

In Istanbul, nature is gentler and more urban: shore walks along the wooded Bosphorus at Bebek or Kandilli, tulips at Emirgan in April, Belgrad Forest trails and cycling on the Princes' Islands. There are no mountains nearby, and leaving the city takes time.

Kas is the better base for day trips, with ancient Lycia all around it. A short ferry crosses to the Greek island of Kastellorizo, and boats reach the sunken city at Kekova and the castle village of Simena. Myra and the church of Saint Nicholas at Demre, and the UNESCO sites of Xanthos and Letoon, are all within about an hour.

From Istanbul, the easy outings are by water: the Princes' Islands, or a cruise up the Bosphorus to Anadolu Kavagi. Bursa is the best town to visit, about two hours away. Edirne and Iznik make long days, and Gallipoli and Troy need an overnight stay.

Istanbul has more for children to do. There are ferry rides, the ships, trains and submarine at the Rahmi M. Koç Museum, Miniaturk, large aquariums and seaside parks on the Asian shore, and children are welcome wherever you go. The drawbacks are crowds, hills, traffic and pushchair-unfriendly pavements.

Kas is calmer and very safe, but it has little made for children. Swimming in town means ladders into deep water, so families with small children head to the shelving sand at Patara or Kaputas. Older children who can snorkel or dive will enjoy it most.

In Istanbul, one rechargeable card covers the metro, the T1 tram through the old city, the Marmaray tunnel under the Bosphorus, the funiculars and the ferries, so you never need a car. The trade-off is packed trams at rush hour and taxis stuck in traffic.

Kas is small enough to walk, though its lanes are steep. Minibuses run along the coast to Kalkan, Patara and Demre, and boats leave from the harbour. For the inland sites, or to travel at your own pace, most visitors hire a car for the winding coast road.

Istanbul is a great place to shop. The Grand Bazaar's covered streets sell carpets, leather, gold and lamps, the Spice Bazaar sits by the Golden Horn, and nearby streets are still grouped by craft. Beyond the old markets are designer labels in Nisantasi, antiques in Cukurcuma and flea markets in Kadikoy.

Kas has one or two bougainvillea-shaded lanes of silver jewellery, linen clothes, ceramics and kilims, which make a nice evening browse and not much more.

Istanbul is generally the cheaper stay of the two. Public transport and ferries cost very little, and so do simit, fish sandwiches and lokanta lunches. Staying in Kadikoy or another residential district keeps the bill low. Costs rise in Sultanahmet, Galata and along the Bosphorus, where hotels and restaurants charge close to southern European levels. Heavily taxed alcohol and the entry fees at the big monuments also add up.

Kas is one of the more upmarket small resorts on the coast. In summer, its hotels, harbourside dinners, dives and boat trips cost about what they would in southern Europe. Back-street pensions, pide bakeries and the minibuses help, and spring and autumn are noticeably cheaper.

Istanbul has a proper stage. The Ataturk Cultural Centre on Taksim Square is home to the state opera and ballet, and summer music and jazz festivals use historic courtyards. Whirling dervish ceremonies take place in old lodges, and fasil musicians play from table to table in the meyhanes.

In Kas, live music means a folk or acoustic set in a bar on a summer evening. Once in a while there is a concert in the little ancient theatre by the sea.

Istanbul offers one of the great bathing traditions. Several of its sixteenth-century hammams by Sinan are still in use, with star-pierced domes, a heated marble slab and an attendant to scrub you down. The city itself is loud, so the rest of the calm comes from tea on a Bosphorus terrace or a slow ferry ride.

Kas relaxes you through its pace rather than its baths: long breakfasts, afternoons on a sun deck, and spring and autumn yoga retreats in the hills. There are hotel hammams and massage rooms, but no historic bathhouses.