Eduardo Di Capua's piece is a quintessential example of Italian salon music capturing the mood of its namesake, the Blue Grotto. It is defined by its sweeping, evocative melodies that demand a resonant, singing touch.
The challenge lies in managing the pedaling to sustain the atmosphere without blurring the harmonic changes.
Comparable difficulty and character — good candidates for what to learn next.
'A grott'azzurra is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 4.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 'A grott'azzurra lasts about 4 minutes.
'A grott'azzurra 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 'O sole mio by Eduardo Di Capua, 'A robba fina! by Eduardo Di Capua, 'A serenata d''e nnammurate by Eduardo Di Capua — see the full similar-pieces list on this page.