Vaes Dothrak is the only city in the Dothraki Sea, located near the far north-eastern edge of the sea. Located in the shadow of a vast peak known as the Mother of Mountains, Vaes Dothrak is a place of peace where the Dothraki khalasars may gather and meet to trade, but not to fight. Therefore weapons are not allowed into Vaes Dothrak. Dothraki holy women, known as dosh khaleen, live in the city and are respected by all Dothraki.
Behind the scenes
The location of Vaes Dothrak in the title sequence of Game of Thrones is erroneous. Later maps show the city lying in the far distant east of Essos, whilst the title sequence map shows it much closer to the western edge of the Dothraki sea. George R.R. Martin did not provide detailed maps for the Dothraki Sea until well into production of the second season.
In the books
In the Song of Ice and Fire novels, Daenerys Targaryen travels east to Vaes Dothrak to gain acceptance and approval for her marriage to Khal Drogo. This frustrates her brother Viserys, since Vaes Dothrak is a thousand miles or more in the "wrong" direction compared to his desire to invade Westeros.
According to the TV series official pronunciation guide developed for the cast and crew, "Vaes Dothrak" is pronounced "VIE-iss Doth-RACK", as opposed to "Vays Doth-RACK", etc. "Vaes" is pronounced as two distinct syllables.