The cap of a Fly Agaric fungus Amanita muscaria.  This attractive toadstool is found in birch and pine woodlands throughout much of the northern hemisphere.   It is poisonous causing severe hallucinations and other unpleasant effects.   No part of it should be eaten.  The bright red cap opens out to around 12-20cm in diameter, and while young is covered in tiny white warts which are actually the remains of a skin or sheath that covered the cap before it opened.  Underneath the cap are white gills.  Fly Agaric toadstools are usually seen from late summer until early winter, when cold weather arrives.