For maven 2 it used to be in
M2_HOME/lib/maven-2.2.1-uber.jar:org/apache/maven/project/pom-4.0.0.xml
But 3.0.x does not have a single jar.
For maven 2 it used to be in
M2_HOME/lib/maven-2.2.1-uber.jar:org/apache/maven/project/pom-4.0.0.xml
But 3.0.x does not have a single jar.
They moved it (without documenting it as usual) to
lib/maven-model-builder-3.0.3.jar:org/apache/maven/model/pom-4.0.0.xml
As for maven 3.5.4
in mac, it's located in
$MAVEN_HOME/lib/maven-model-builder-3.5.4/org/apache/maven/model/pom-4.0.0.xml
But you have to unzip
the maven-model-builder-3.5.4.jar
first, where the super pom hides.
It's documented in Sonatype's Maven reference book, which for some reason doesn't turn up easily in Google results: http://books.sonatype.com/mvnref-book/reference/index.html