Rachmaninoff's legendary, highly virtuosic cadenza for Liszt's second Hungarian Rhapsody. It is famous for its extreme difficulty and massive, pianistically demanding textures.
Mastering the double-note runs and massive chordal climaxes requires immense hand stamina and technical facility.
Comparable difficulty and character — good candidates for what to learn next.
Cadenza to Liszt's Hungarian Rhapsody No.2 is rated Henle level 9 of 9 — virtuoso repertoire, roughly concert / virtuoso level.
You should be comfortable at Henle level 9 — meaning you can already play level 8–9 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 Cadenza to Liszt's Hungarian Rhapsody No.2 lasts about 2 minutes.
Cadenza to Liszt's Hungarian Rhapsody No.2 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 Piano Sonata No. 2 in B-flat minor by Sergei Rachmaninoff, Variations on a Theme of Corelli by Sergei Rachmaninoff, Hungarian Rhapsody No. 2 in C-sharp minor by Franz Liszt — see the full similar-pieces list on this page.