Where to put favicon for a scala Spray application (i.e. what is the root of the site?)?

Internet says I should put my favicon.ico in the root of the site to stop Spray from clogging my logs with huge stacktraces. I don't know what the root of the site means, particularly in the context of a RESTful spray application.

Suppose my project is in ~/src/my-project - I build it (sbt assembly), and run it from this location, where should I put the favicon.ico?? I tried putting in ~/src/my-project but I still get the stacktrace.

NB: it only throws the exception if I directly access the API from my browser (rather than via the actual front end of our website).