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A Weekend in the İğneada Floodplain Forest and Dupnisa Cave
Cultural

A Weekend in the İğneada Floodplain Forest and Dupnisa Cave

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In the north-eastern corner of Thrace, a few kilometres from the Bulgarian border, the streams running down from the Istranca (Strandzha) Mountains spread across a wide plain before they reach the Black Sea.

Demirköy, Kırklareli
Cultural
Radar Editör
September 24, 2026

About Trip

In the north-eastern corner of Thrace, a few kilometres from the Bulgarian border, the streams running down from the Istranca (Strandzha) Mountains spread across a wide plain before they reach the Black Sea. The forests here flood every winter; locally they are called longoz, and the one at İğneada is the most important surviving example in Turkey. In the hills of the same district lies Dupnisa, a cave system that has been forming for some four million years, with an underground river running through it. Lakes, dunes, flooded forest and a cave full of bats make a good pairing for a nature trip that is far from Istanbul but fits into two days.

Getting There from Istanbul

According to the Demirköy District Governorate, İğneada is about 250 kilometres from Istanbul and 97 kilometres from Kırklareli; the drive takes around three hours. By car, the most practical route runs through Saray and Vize to Poyralı and Demirköy, then down to İğneada. If you have already visited Kıyıköy and Vize, you will know part of this road.

It is possible by public transport too, changing at Silivri, Çorlu, Lüleburgaz, Pınarhisar and Demirköy, but the connections make it a long journey, and reaching Dupnisa Cave without a vehicle is difficult. A car is the most comfortable option for this trip. Check current schedules with the bus companies before setting off.

What a Longoz Is and Why It Matters

Longoz is the local name for alluvial forest that floods seasonally. According to the nature conservation authority's description, İğneada's forests formed as streams from the Yıldız (Istranca) Mountains deposited alluvium on the coastal plain, which is then flooded for part of each year. The area combines freshwater and saltwater lakes, coastal dunes, fresh and brackish marshes, flooded forest and mixed deciduous woodland of oak, beech, hornbeam, ash and alder. Climbing plants twisting around the trunks are one of the classic sights of the longoz.

Separate pieces once protected as a nature reserve, natural site and wildlife protection area were united into a single national park on 13 November 2007. Turkey's 39th national park, İğneada Floodplain Forests National Park covers about 3,155 hectares within the boundaries of İğneada. The Demirköy District Governorate stresses that the area lies on major Western Palearctic bird migration routes and that its lakes and reed beds are a vital stopover for migrating birds.

Lakes and Dunes

There are five lakes in the park. The largest is Lake Mert, about 266 hectares, formed where the Çavuşdere stream meets the sea south of İğneada. Lake Erikli to the north is really a lagoon, cut off from the sea by drought in summer. Small Lake Saka lies to the south, squeezed between the forest and the dunes, and Lakes Hamam and Pedina sit further inland.

The dunes along the coast are split in two by the town. The dunes total some 10 kilometres; the southern stretch runs from the mouth of Lake Mert to beyond Lake Saka, reaching 50-60 metres wide in places. This narrow strip separates the sea from the forest, marshes and lakes, and it supports plants specific to the south-western Black Sea coast. Take care not to step on the dune plants and stay on the paths.

What to Do in the Longoz

The main activities are photography, birdwatching, nature walks and picnics. Recorded birds include the white-tailed eagle, green woodpecker, black stork, kingfisher, grey heron and hoopoe; mammals include wildcat, wild boar, roe deer, badger and otter. For birdwatching, wait quietly by the lakeshores early in the morning, and bring binoculars. Some forest tracks can be under water after rain, so confirm your walking route with the park administration or on the local information boards.

İğneada itself is a beach town. According to the Kırklareli Provincial Directorate of Culture and Tourism, it has a sandy beach 40-50 metres wide and 10 kilometres long, with many guesthouses nearby.

Dupnisa Cave

On the second day, head inland to Dupnisa Cave, about six kilometres south-west of the village of Sarpdere. The cave is 26 kilometres from Demirköy and 60 from Kırklareli, in thickly wooded country where the Rezve stream, which forms the border between Turkey and Bulgaria, cuts deep valleys through the Istranca Mountains. The name is said to come from a Bulgarian word meaning hole.

According to the Culture Portal, Dupnisa is a system of three connected caves on two levels, 2,720 metres long in total. The Dry Cave and the Maiden's Cave form the upper level; 50-60 metres below lies the Water Cave, with an underground river flowing through it and pools more than 2 metres deep in places. The entrance is 345 metres above sea level. The highlights are stalactites, stalagmites and columns ranging from milky white to red and every shade of brown, along with curtain and flag formations and dripstone pools. The upper level is warmer and drier, while the main gallery is cool and damp at around 10-12 degrees, and the difference creates a noticeable draught between them.

The cave opened to visitors in June 2003. About 450 metres of the Dry and Water caves can be visited on walkways with lighting. The provincial directorate notes that day picnics and nature walks are possible around the cave.

Bats and Visiting Seasons

Dupnisa is an important bat habitat. According to the Kırklareli Provincial Directorate of Culture and Tourism, about 60,000 bats of 11 species live here, along with 184 species of cave invertebrates. Visiting rules therefore change with the seasons. The Maiden's Cave, where bats are densest, is completely closed to visitors. The Dry Cave, which has no bats, is open all year. The Water Cave closes from 15 November to 15 May because of the bats.

In short, if you want to see both sections, plan your trip between 15 May and 15 November. Keep quiet inside, do not shine lights at the bats and stay on the walkways.

A Suggested Two Days

  • On day one, leave Istanbul early and reach İğneada around midday.
  • In the afternoon, walk by Lake Mert and through the forest.
  • In the late afternoon, go down to the southern dunes or İğneada beach, and spend the night in İğneada.
  • Early on day two, watch birds around Lake Erikli or Lake Saka.
  • Towards midday, drive via Demirköy to Dupnisa Cave; allow two hours for the cave and the forest around it.
  • Head back to Istanbul in the afternoon.

The Fatih Iron Foundry, on the provincial directorate's list of heritage sites, is also in Demirköy; stop if you have time.

Season and Timing

The best periods are late May to late June and September to late October. Both caves are open and the forest is either lush green or in autumn colours. Spring and autumn are also good for migrating birds. In winter and early spring the flooded longoz is impressive, but the Water Cave is closed and forest tracks can be muddy. In summer İğneada welcomes beach holidaymakers, so book accommodation ahead.

Practical Notes

  • The cave is cool and damp whatever the season; bring a jacket and non-slip shoes.
  • Check Dupnisa's opening days and hours with the Kırklareli Provincial Directorate of Culture and Tourism.
  • In the national park, follow the rules on fires, plant picking and entering the dunes.
  • Fill up on fuel and food in Demirköy; the road to the cave is wooded and sparsely settled.
  • You are close to the border, so carry ID.

Sources

Location - A Weekend in the İğneada Floodplain Forest and Dupnisa Cave

Trip Info
CityDemirköy, Kırklareli
TypeCultural
DateSeptember 24, 2026
SourceRadar Editör
Radar TürkiyeAuthorRadar TürkiyeVisit SourceGet Directions