The Firth of Forth is an estuary located in the southern lowlands of Scottland. "Firth" is closely related to the word "fjord", which is an "narrow inlet" of water. The firth is populated by many small towns and industrial complexes. The firth is also home to some 90,000 birds every year that come to breed. Mentioned by Dorothy Wordsworth in Recollections in a tour made in Scottland,  Wordsworth is aware of the firth's location on her way to Edinburgh. She says, "Arrived at Edinburgh a little before sunset. As we approached, the Castle rock resembled that of Stirling—in the same manner appearing to rise from a plain of cultivated ground, the Firth of Forth being on the other side, and not visible." Historically, the Firth of Forth has been named in Welsh and Norse mythical literature.