This is Franz Liszt's virtuosic piano transcription of the 'Elsa's Dream' scene from Wagner's opera Lohengrin. It is a masterwork of transcription, transforming vocal lines into grand, orchestral-like textures.
Achieving the correct balance between the operatic vocal melody and the opulent, wide-spanning accompaniment is critical.
Comparable difficulty and character — good candidates for what to learn next.
Aus Lohengrin (S.446) is rated Henle level 8 of 9 — concert repertoire, roughly diploma level. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 8 — meaning you can already play level 7–8 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Aus Lohengrin (S.446) lasts about 6 minutes.
Aus Lohengrin (S.446) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Aus Lohengrin, Wagner by Franz Liszt, Aus Lohengrin, by Wagner by Franz Liszt, Un sospiro by Franz Liszt — see the full similar-pieces list on this page.