跡 - He Left Behind Red Footprints

Readings & Meanings:

あと

セキ

traces, marks, remains

Common Usage:

足跡

遺跡

Examples:

この辺りには時々熊の足跡が残っている。

この遺跡には昔の人が食べた貝の殻がたくさん残っている。

Translations:

In this area, sometimes bear footprints are left.

In these ruins are the shells from shellfish eaten by people long ago.

Bonus:

Guess what? There's a radical here, too! 足 appears in many kanji. Check out Jim Breen for a complete list. http://www.csse.monash.edu.au/~jwb/cgi-bin/wwwjdic.cgi?1S

References:

http://www.thejapanesepage.com/kanji/kanji/a.htm