At this locaction above a rock grotto originally a small copy of the Habsburg castle from Switzerland was planned around 1800.

In 1805 Widemann wrote: "In the upper half of the lake there is a rock, forty and eight fathoms high, through whose dark gorges and twists one can raise oneself into what will once become a castle that will become the image of the now so famous Habsburg and is also to bear this name. The charming views of the original castle painted by Rahn will adorn the rooms of the granddaughter, and in the majestic grotto of the rock, which receives light through the castle courtyard, the busts of all the Habsburg emperors will stand."

These ambitious plans were not realised, although at about that time a model, which could be taken apart, of the Habsburg featuring verses by a Swiss poet was displayed on the tournament site and admired with great interest by the imperial family. The architect Hohenberg was also commissioned with planning in this respect, but his plans then seemed too costly to the imperial house. It is likely that the early death of Empress Maria Theresia of Naples brought a sudden end to these considerations.

Even in the last year of her life, she had been occupied with another project for the construction in miniature of the ruins of Pompeii in Laxenburg.

GrotteWith Franzensburg and Habsburg, the gardens of Laxenburg would have received an iconographic counterpoint: The "new-old" fortress and the "old-new" ruins would have complemented each other and meant a sentimental and exciting representation of the glorious history of the house. The past, present and future of the dynasty would thus have been represented dialectically in a picturesque pond landscape. It is interesting that during the period in which the Franzensburg came into being, a trend from the initially strong emphasis of ruins to the completed character of the new is to be observed, which is doubtless related to the "Ruins of Habsburg" project. Today, the grotto stands without the ruins of Habsburg and is therefore somewhat reduced in terms of its contents. However, it bears important witness to the understanding of nature and art around 1800.

At the foot of the grotto there is a little romantic hollow, the so-called Sophiental or Sophies Valley. This dreamlike place was and is especially rich in botanic treasures. There you can admire e.g. the oriental spruce, the Spanish fir, Syrian juniper and some yew trees. At the heart of the Sophiental there has always been a copper beech, which was replanted in 2008 to preserve the identity of the place.