Saint Michael's Cave is a series, or network of caves made of limestone, which are found on the Rock of Gibraltar. St Michaels Cave is located on what is called the Upper Rock, inside the Upper Rock Nature Reserve of Gibraltar.
The cave was created by the slow seepage of rainwater through the rock, which turned into a carbonic acid solution that actually dissolved the rocks of the cave. The process made the tiny cracks of the geological faults of Gibraltar grow into very long passages and deep caverns over the thousands of years of its formation. The Cathedral Cave, part of St Michaels cave was at one time thought to be bottomless, and was long spoken of in the legends of Gibraltar.
The Rock of Gibraltar has long been considered to be one of the pillars of Hercules, and this too adds to the mystique and legend, and since it hosted the cave, the caverns themselves were thought to be the Gates to Hades, or Hell, an entryway to the Underworld where the dead rested.
In the latter part of 1974, proof that the cave was known to and used by prehistoric men was made clear with the finding of art on the cave walls, showing an ibex drawn there that was traced to the Solutrean period (dating the cave art to about 15-20 thousand years ago), but later, two Neanderthal skulls that were found in Gibraltar tell us that this cave could have been discovered and used as early as 40,000 BC.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.