The Loosdrechtse Plassen form a large nature reserve where water and water sports predominate. The ponds form the central part of a protection zone for birds, other animals and plants. The water-rich area was created from peat, as a result of which water gained more and more ground. The lakes consist of different waters that are separated from each other by dikes and islands. By definition, the Eerste to Vijfde Plas together form the Loosdrechtse Plassen, whether the area also consists of other waters is up for debate, because the boundary of the area is not clearly demarcated. National monument Kasteel Oudaen is the first sight you encounter. This former knight's court town was built around 1300. The very old house was owned in the fifteenth century by a family who also owned the city castle of the same name in Utrecht. The original castle Gunterstein also dates from about 1300. The complex is named after its first owner. In 1511 the castle was demolished by residents of Utrecht who used the stones to restore the Bemuurde Weerd of Utrecht. The second building was built in 1518, but it was set on fire by the French in 1673. In 1680, the new owner Magdalena Poulle had the country estate built as it still looks today. Fort Tienhoven was built between 1848 and 1850 to close off the Tienhovense Vaart. The fortress defended the inundation quay, a dam lock and a crow lock against hostile traffic over water. The fort is not accessible, but even from the outside the fort is an imposing building. The next beautiful building is that of Sypesteyn Castle. The building is said to have been built around 1288, but the oldest found foundations of this complex date from around 1500. In 1589 the house is destroyed by skirmishes and shortly after the ruins have been restored, fighting between French troops and soldiers of the stadtholder destroys it. castle again. Around 1900 the estate was bought by esquire Henri van Sypesteyn. Using material from demolished historic buildings and churches, he builds a sober ancestral castle on the foundations of the ruins. This castle is set up as a museum about the family, but the museum also houses collections of arts and crafts. The castle garden is also beautiful: the park is more than five hectares in size and a (castle) garden, a maze and an orchard have been laid out. They are separated by hedges, canals and ornamental fences from old country estates. When you arrive at Slot Zuylen, you will see that the castle is located in a small park. The territory of one and a half hectares is fenced with a snake wall. This wall is 120 meters long and is on the list of national monuments. There are several national monuments on the site: the quay walls, a culvert, a bridge, the gatehouse, the corner tower, the coach house, the gardener's house, the castle farm, the wood storage and wagon shed, the playhouse, the iron fencing and a vegetable garden are all of great importance. cultural-historical value. The history of the first castle goes all the way back to the thirteenth century, when a keep was built here. The castle became bigger and more extensive and in 1752 the castle was last radically renovated. Today it houses a museum. You will then come across two fortresses: Fort De Gagel and Fort aan de Klop. Both are parts of the New Dutch Waterline. Fort De Gagel was built between 1819 and 1821, with L-shaped earthen walls with emplacements for artillery, which were raised behind excavated canals. From 1848 the fort was expanded considerably. Among other things, a bombproof guardhouse of 256 m2 was built. A moat was also built around this guard house and this building was also equipped with (heavy) artillery. Forty years later, the fort was reinforced again, filling in the moat around the guard house and drastically rebuilding the inside of the guard house. The state of the guard house is now the same as after the renovation in 1880. Fort aan de Klop was also built in 1819. This fort is strategically located and defended Utrecht. This fort is exploited for recreational use: you can camp there, drink a cup of tea in the tea house or spend the night in an inn. Between the restored historic sheds and the old guard house, you can imagine yourself back in time! The last point of interest during your tour is Slot Zuylen. The castle is located in a beautiful park, on a territory of one and a half hectares, which is bordered by a snake wall. This wall is 120 meters long and is on the list of national monuments. There are several national monuments on the site: the quay walls, a culvert, a bridge, the gatehouse, the corner tower, the coach house, the gardener's house, the castle farm, the wood storage and wagon shed, the playhouse, the iron fencing and a vegetable garden are all of great importance. cultural-historical value. The history of the first castle goes all the way back to the thirteenth century, when a keep was built here. The castle became bigger and more extensive and in 1752 the castle was last radically renovated. Today it houses a museum.