Esoteric Buddhism (Vajrayana) imagines two realms or worlds (dhatu), the Diamond Realm (Vajradhatu) and the Womb Realm (Garbhadhatu), mystical spaces that represent certain principles, different bodies of the Buddha, and various celestial Buddhas and bodhisattvas. They could be called “buddhaverses.” The two realms correspond to the concept of the Two Truths as presented by Nagarjuna.
And they are presented graphically as mandala, which are diagrams, geometric patterns and art depicting or mapping out a buddhaverse and are used primarily as an aid to meditation. In Japanese Buddhism, mandala is frequently used in the Shingon and Tendai schools.
The two realms are not separate (just as the Two Truths are not really two) but rather manifest one reality, and this oneness is represented in the Mandala of the Two Realms. The individual mandala are the Diamond Realm and the Womb (or Matrix) Realm Mandala. The Womb Realm (Taizokai) symbolizes the world of embryonic truth, and the Diamond Realm (Kongokai), the world of ultimate truth.
As you can see from the above image of the Womb Realm Mandala, various Buddhas and celestial beings are grouped together in halls or courts surrounding the central 8-Petal Hall and the central figure, the cosmic Buddha Dainichi (Mahavairocana), representing the Dharma Body of the historical Buddha.
Recently I put together a piece of ambient music that to me sounds like the Womb Realm. Ambient is defined as “a genre of instrumental music that focuses on sound patterns more than melodic form and is used to create a certain atmosphere or state of mind.”
You can also listen to the piece on my YouTube channel.