Heimerdinger was born in Bandle City, the capital of Yordle Land. Yordle Land is the mountained off coastal strip on the southeast corner of Runeterra’s main continent where, unsurprisingly, most yordles live.
Yordles, for those that don’t know are a race of small animal/oompa-loompa style humanoids. They’re roughly 3 feet tall, enjoy socializing and pranks, excel at creating complex tools, and require constant socialization with other friendly individuals, preferably yordles.
Source: The Game Website.