Merchant's Arch
Merchant's Arch is a bar near the Ha'Penny Bridge in Dublin, Ireland, which dates back to 1821.
Map
The following is a map of Merchant's Arch:

Network Graph

Most Common References
In this location, an allusion to Edward Fitzball was made.
Edward Fitzball (1792-1873) was an English playwright who specialized in melodrama. Two of his works were "Floating Beacon" and "Pilot."
This Location in Ulysses
The only allusion made in this location was a reference to Fitzball, who was particularly talented at writing nautical dramas. Perhaps Joyce thought of this location in a dramatic, literary sense and in a seafaring way.