Most people don’ t realize that the bright spots below a tree in the grass are actually images of the sun formed by small holes created through overlapping leaves in the tree’s branches. Because the sun is a sphere, the images are also circular (depending of the angle of the surface).
A similar situation occurs when the sun shines through the small holes in blinds – round images of the sun are projected against the foor or wall. The images become interesting when the sun’s disk is obscured by something, e.g. the moon during a solar eclipse or trees when the sun is rising or setting on a wooded horizon.
Here are some images I took in 1999 when we were living in an apartment that would have optimal conditions for observing such sunrises:
Here is a link to the sunspot drawing from the Kanzelhöhe observatory from this day: sunspot drawing 22.12.1999
During the 2015 solar eclipse I used two pieces of cardboard to project the sun through two holes, one 5mm in diameter, one 2mm. The bigger hole makes a brighter image, but the image from the smaller hole is much sharper:
This is actually a safe way to observe a solar eclipse!