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I found in here this document. I read it but I keep wondering how to define a Polygon with 3 rings in WKT?
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Well-Known Text (WKT) is an ASCII representation of a spatial object.
Well-known text (WKT) is a text markup language for representing vector geometry objects on a map, spatial reference systems of spatial objects and transformations between spatial reference systems.
Well Known Text (WKT) is an Open Geospatial Consortium (OGC) standard that is used to represent spatial data in a textual format. Most OGC-compliant systems support Well Known Text.
A polygon consists of one or more rings. A ring is a connected sequence of four or more points that form a closed, non-self-intersecting loop. A polygon may contain multiple outer rings. The order of vertices or orientation for a ring indicates which side of the ring is the interior of the polygon.
You can use either the POLYGON or the MULTIPOLYGON type, but make sure the outer container ring is listed first followed by the inner hole rings. The orientations of the inner rings are not important since holes are explicit in the syntax.
X & Y are space separated, coordinates are comma separated, and ring extents are limited by parentheses and separated by commas. Polygons (outer ring plus any inner rings) are also limited by parentheses.
Finally, inner rings cannot cross each other, nor can they cross the outer ring.
Examples:
POLYGON ((10 10, 110 10, 110 110, 10 110), (20 20, 20 30, 30 30, 30 20), (40 20, 40 30, 50 30, 50 20))
MULTIPOLYGON (((10 10, 110 10, 110 110, 10 110), (20 20, 20 30, 30 30, 30 20), (40 20, 40 30, 50 30, 50 20)))
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