Separate to the PostGIS extension currently supported by hibernate-spatial, there are also built-in geometric types and functions.

https://www.postgresql.org/docs/current/datatype-geometric.html
https://www.postgresql.org/docs/current/functions-geometry.html

Note that generated SQL should use the operators rather than their equivalent functions (e.g. @> instead of box_contain_pt) otherwise the query planner will not make use of relevant indexes.