The view from the observation deck over the Messel Pit is quite uninteresting, you just see a big hole of about 500 meters in diameter. That this place is an important palaeontological site and that excavations still take place is not evident.

As the other reviewers I also recommend to take a guided tour. There are tours every day from April to October. Several years ago I attended the one-hour tour and on my last visit (in 2012) the two-hours tour. Both guides were excellent. In fact, there is not much to see, but they made the best of it. I learned a lot about the origin of the fossils, the geology, and the recent history of the pit (oil shale mining, the proposed garbage dump which was prevented by public opposition, and finally the WH inscription). During the two-hours tour we walked to the artesian well at the bottom of the pit and we also went past the site of the current excavations. The guide explained the technique: a large block is cut out from the oil shale and is carefully split with a flexible blade. If a fossil is found, it must be immediately stored in water to protect it from drying out. We were also searching for fossils in the overburden. That was a lot of fun, not only for the children. And with some luck you can find a part of a plant or a small insect.

The fossils were formed 47 million years ago (Eocene) over a period of 1.7 million years. At that time the place was a rainforest. A volcanic eruption created a water-filled crater (maar), which was refilled by sedimentation of dying algae, dead animals and mud. Due to the relatively great depth in relation to the small surface, water exchange by convection occurred only in the upper layers. This led to a lack of oxygen at depth and therefore dead animals and plants were preserved and petrified in deeper layers. The existing pit is the result of the oil shale mining and is about 70 metres deep. The fossil layer is in total about 200 metres deep, so there is still plenty of work for the palaeontologists.

Messel is known primarily for the ancestral horses, of which about 70 specimens have been found. There are also other mammals, crocodiles, many birds and bats. Large animals are rare, but almost every day they find a bowfin, every hour a small fish, and countless insects and part of plants. The state of conservation of the Messel fossils is outstanding. Sometimes even parts of the soft tissue were preserved, like parts of fur or feathers, stomach contents, feces and even wings of insects along with their original colouring.

In 2010, a new visitor centre was opened. The permanent exhibition informs about volcanism, geology, the formation of the pit and the research activities. However, the entrance fee of 10 Euros (without the tour to the pit) is relatively high. There are also about a dozen fossils (photo shows a turtle), but the best examples can be seen in the Landesmuseum in Darmstadt. The museum in Messel also shows some fossils. On some weekends in summer, they demonstrate how a fossil is prepared. At our visit we were able to watch the preparation of a turtle. The process is really complicated, the preparation of a turtle takes about 3 weeks.

All in all, the Messel Pit is worth a visit, they have done a lot to make a visit interesting, and the guided tours are excellent.