Chopin's Ballade No. 3 in A-flat major is a masterwork of Romantic piano literature inspired by Mickiewicz's poetry. It is distinguished by its seamless integration of two contrasting themes and its sophisticated, weaving contrapuntal textures.
The primary challenge is balancing the delicate voicing in the right hand against the fluid, complex accompaniment figures.
Comparable difficulty and character — good candidates for what to learn next.
Ballade No.3 (Op.47) 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 Ballade No.3 (Op.47) lasts about 8 minutes.
Ballade No.3 (Op.47) 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 Nocturne in F-sharp major, No. 2 by Frédéric Chopin, Ballade No.1 by Frédéric Chopin, Ballade No.4 by Frédéric Chopin — see the full similar-pieces list on this page.