城 is a Japanese kanji written with 9 strokes, listed here under the keyword “castle”. It is built from 土 (soil) and 成 (turn into). In Remembering the Kanji by James W. Heisig it is frame 387.
On KumiJi Glyph Explorer, open the parts search and type “soil” + “turn into”. 城 is among the results, together with every other character containing the same shapes.
Open 城 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.