The natural monument "Thick Island" is located in the Vyborg district, 2 km west of the city of Vysotsk, 7 km from Vyborg in the south-west.
"Island Thick" was organized as a regional geological natural monument in 1976. Its area is 54 hectares. The purpose of the monument of nature - the preservation of the original forms of relief: "mutton foreheads" and unique granite outcrops on the surface of rapakivi. Protected Objects in the "thick Islands" - a relief "mutton foreheads" and granites rapakivi.

"Mutton foreheads" is a smooth movement of the glacier rocks which are composed of bedrock extending to the surface. A particularly smooth and gentle slopes are, who were facing the movement of the glacier slopes on the other hand are often steep and uneven. Groups of small "mutton foreheads" is also called curly rocks. Mutton foreheads found in the mainland and mountainous areas of ancient and modern glaciation. "Mutton foreheads" is especially prevalent in the territory of the Baltic Shield.

Granite rapakivi (in Finnish "rotten, crumbling stone") - a kind of granite rocks with an acid composition. Granite Rapakivi consists of 40% orthoclase, idiomorphic 30% quartz, 20% oligoclase. also contains a small amount of impurities minor accessory minerals (2%), such as amphibole, orthite, diopside, sphene, apatite, magnetite and others. On the cut Rapakivi clearly visible large grain of the granite. In terms of longevity, he is inferior to the samples of fine-grained granite. This type of granite can be painted in different shades of brownish-pink color, sometimes there is a greenish, reddish and black rapakivi. In addition to the Leningrad Oblast and Karelia granite rapakivi widespread in Finland, Sweden, the Ukraine (Cherkasy region). By the way, Alexander Column and the monolith under the "Bronze Horseman" - from this stone.

The territory of the natural monument "Island Thick" is promising for eco-tourism as a separate entity, as well as for the organization of tourist routes to the protected natural monuments of the Gulf of Finland and the Karelian Isthmus.

Island Thick plan has the shape of a horseshoe. The northwestern part of the island - a granite rock about 30 m in height, stretching on the floor and smoothed kilometer glacier - a gentle slope "mutton foreheads." The eastern coast of the island of dense - steep (the height of the cliff is about 20 m). This is due to a tectonic disturbance. In other parts of the island can be found thick polished rocks. On the surface clearly distinguished large ovoids - edged crystals of mica and quartz rounded crystals of feldspar, which are typical for rapakivi granites.

At the center of the island juts thick colorful bay - a favorite place of parking boaters. Water open spaces and lots of wooded islands with rocks, rugged coastline, "mutton foreheads" long and narrow bays - all this forms the picturesque landscape of the archipelago, which differentiates the northern coast of Scandinavia, and is not typical for other areas of the Leningrad region.

On the territory of the natural monument it is prohibited to develop and produce granite campfires.