Łebsko Lake
Łebsko Lake (German: "Lebasee" ) is a coastal lake in the Pomeranian Voivodeship of Poland.
 It is the part of Słowiński National Park.
 However, it was never a part of the Baltic sea.
 It was formed because of the rise in the sea level and the flooding of the local meadows.
Coatepeque Caldera
Caldera De Coatepeque (Nahuatl "cōātepēc", "at the snake hill") is a volcanic caldera in El Salvador in Central America.
 The caldera was formed during a series of minor rhyolitic explosive eruptions between about 72,000 and 57,000 years ago.
 Since then, basaltic cinder cones and lava flows formed near the west edge of the caldera, and six rhyodacitic lava domes have formed.
 The youngest dome, Cerro Pacho, formed after 8000 BC.
Masaya Volcano
Masaya is a caldera located in Masaya, Nicaragua, 20 km south of the capital Managua.
 It is Nicaragua's first and largest national park, and one of 78 protected areas of Nicaragua.
 The complex volcano is composed of a nested set of calderas and craters, the largest of which is Las Sierras shield volcano and caldera.
 Within this caldera lies a sub-vent, which is Masaya Volcano "sensu stricto".
 The vent is a shield type composing of basaltic lavas and tephras and includes a summit crater.
 This hosts Masaya caldera, formed 2,500 years ago by an 8-km³ basaltic ignimbrite eruption.
 Inside this caldera a new basaltic complex has grown from eruptions mainly on a semi-circular set of vents that include the Masaya and Nindiri cones.
 The latter host the pit craters of Masaya, Santiago, Nindiri and San Pedro.
 Observations in the walls of the pit craters indicate that there have been several episodes of cone and pit crater formation.
Sinnott Memorial Observation Station
The Sinnott Memorial Observation Station is a sheltered viewpoint built into the caldera cliff 900 feet above Crater Lake in southern Oregon, United States.
 It is located near the Rim Village Visitor Center in Crater Lake National Park.
 The structure includes a small natural history museum with exhibits that highlight the geologic history of Mount Mazama and the formation of Crater Lake.
 The building was officially dedicated as the Nicholas J. Sinnott Memorial Observation Station and Museum; however, it is commonly known as the Sinnott Memorial Overlook or Sinnott Viewing Area.
 It is architecturally significant because it was the first National Park Service building constructed specifically as a museum and the first structure built in Crater Lake National Park using rustic stone masonry construction.
 It is listed on the National Register of Historic Places as Sinnott Memorial Building No. 67.
Crater Lake National Park
Crater Lake National Park is a United States National Park located in southern Oregon.
 Established in 1902, Crater Lake National Park is the fifth-oldest national park in the U.S. and the only national park in Oregon.
 The park encompasses the caldera of Crater Lake, a remnant of a destroyed volcano, Mount Mazama, and the surrounding hills and forests.
Słowiński National Park
Słowiński National Park (Polish: "Słowiński Park Narodowy" ) is a national park in Pomeranian Voivodeship, northern Poland.
 It is situated on the Baltic coast, between Łeba and Rowy.
 The northern boundary of the park consists of 32.5 km of coastline.
Valles Caldera
Valles Caldera (or Jemez Caldera) is a 13.7 mi wide volcanic caldera in the Jemez Mountains of northern New Mexico.
 Hot springs, streams, fumaroles, natural gas seeps and volcanic domes dot the caldera floor landscape.
 The highest point in the caldera is Redondo Peak, an 11253 ft resurgent lava dome located entirely within the caldera.
 Also within the caldera are several grass valleys ["Valle(s)"] the largest of which is Valle Grande ( ), the only one accessible by a paved road.
 Much of the caldera is within the Valles Caldera National Preserve, a unit of the National Park System.
Lake Gardno
Gardno (German: "Garder See" ) is a lake in the Słowińskie Lakeland in Pomeranian Voivodship, Poland.
 It is the part of Słowiński National Park.
 Its area is 24.69 km2 .
 It is 6.8 km long and 4.7 km wide.
 Maximum depth is 2.6 m.
Lake Tōya
Lake Tōya (洞爺湖 , Tōya-ko ) is a volcanic caldera lake in Shikotsu-Toya National Park, Abuta District, Hokkaidō, Japan.
 It is a part of "Toya Caldera and Usu Volcano Global Geopark" which joins in Global Geoparks Network.
 The stratovolcano of Mount Usu lies on the southern rim of the caldera.
 The lake is nearly circular, being 10 kilometers in diameter from east-west and 9 kilometers from North-South.
 The lake's biggest town, Tōyako is located on its western shore.
 The town Sōbetsu is located on the other side of the lake.
Slovincian Coast
Slovincian Coast (Wybrzeże Słowińskie, Polish; Słowińsczé Ùbrzeżé, Kashubian) (313.41) - a mesoregion, the northernmost part of the Koszalin Coast, with an area of 1132 km².
 The highest hill is Rowokół, at 114,8 metres above sea level.
 The coast stretches from the west at Kołobrzeg, up to the east at Karwia.
 The landscape mainly compromises of dunes, marshland and lakes (such as Łebsko Lake).
 The region is sparsely populated, the largest towns are: Łeba, Ustka and Darłowo.
 In the region of the Slovincian Coast is the Słowiński National Park.

Question: Which formation, Łebsko Lake or Coatepeque Caldera, is part of the Słowiński National Park?
Answer: Łebsko Lake