For a long time, Cais sodré was the elected area for most sailors docking in Lisbon Harbour. With a Street filled with Clubs named after Port cities, it was also an area with a very "bas-fond" type of ambiance, heavily loaded and with a lot of prostituition.
Nowadays, much like the soho in London, and other similar originally lower class places across the world, this area is being taken over by a trendier crowd, with remodeled traditional cafés, burlesque and vintage attractions co-existing with older rock clubs where you can find from the hardcore biker to young artists and professionals and college professors, in a wonderfull mix.
Viking is a club that has stayed true to its origins, mantaining to this day 1 dancer that performs a strip show (1 am wed and 1 am and 3 am on weekends) on a small stage. For this reason it is very popular as a stopping place for bachelour parties, usually for young professionals that are not interested in going to a heavier strip club or lapdances and such, but that still want a hint of more naughty fun, and where girls can also feel confortable.
The rest of the time it's a dance club with diverse music and crowd.
The staff is also diverse and I love the fact that it is not just composed of young barmaids and bartenders, but that still keeps older people that have been working there for years and years and that are not only very friendly but help maintain the character of the place, like the lady in the cloak room / waitress. :)
Even if it's not your usual cup of tea, it's still very much worth a visit, as you can experience this more alternative ambiance, but still be in a perfectly safe environment.