There are 31 realms of existence described in the Pali Canon, which can be found detailed in such books as
this one.
Modern practitioners have noticed various experiences out past the 8th jhana that seem a remarkably nice combination of factors that yet are not the classic combination of factors noted for the first four jhanas.
Some, such as and particularly Kenneth Folk, have posited that these jhanic experiences which combine elements in unusual ways, are what were being discussed as correlating with certain realms, in particularly one of the Pure Abodes, see linked book above, starting on page 43, realms 27-31. In fact, Kenneth Folk has considered the term "Pure Land Jhanas" as his proprietary term which he discovered yet also the correct interpretation of a traditional term at the same time.
Yes, it is definitely possible to build your own jhana through concentration. One of the problems with being sure that certain experiences may line up with or correlate with various canonical realms is that, other than the traditional realms' lack of precisely defining qualities and factors, there is the problem that those with strongly developed concentration and technical jhanic skill who can cultivate flavors of jhana that combine various qualities in custom combinations that are not found explicitly in the old texts.
And yet, the texts do list the depths of concentration as being one of the four imponderables, those things that defy total categorization and description, being too vast to be bound entirely by language and concepts.
The old texts also list the 31 realms, which provide intriguging inspiration for creative jhanic experiences, as well as possible confirmation that the remarkable jhanic experiences found today by some practitioners may have also been found then and described as realms.
