Long Canal

"So give me a kiss by the Long Canal, and give me two kisses in Salty Town, for we're going to die tomorrow! The bareheaded beggar, the king with his crown..."

- Mace Tyrell serenades Tycho Nestoris

The Long Canal is a large canal, and one of the main waterways in Braavos. Arya Stark uses it to reach the House of Black and White upon her arrival in Braavos.

Mace Tyrell performs a boisterous Braavosi ballad in which the Long Canal is mentioned to an irate Tycho Nestoris.

In the books
In the A Song of Ice and Fire novels, the Long Canal and it's location are presumably the same, as Arya also reaches the House of Black and White via it.

Mace Tyrell never travels to Braavos in the timeline of the books, and so his tuneless rendition of the Braavosi shanty is never heard.