Citybanan (City Line), a six kilometer long tunnel deep under the city which reroutes the commuter train line away from the regular train lines. Construction started in 2006 and the line finally opened this past Monday! Cost for the project is estimated to land at around 20 billion SEK.
Central Train Station in downtown Stockholm was completed in 1871 and all southbound train traffic goes across a bridge and through the old town (Gamla Stan/Riddarholmen). This all worked fine when it was used solely by regional/international trains, but since then Stockholm has constructed a large system of commuter trains servicing the suburbs and this has become a bottleneck, especially for the southbound traffic. Expanding the tracks was vetoed by the government due to the historically sensitive buildings in the area. The solution? Reroute the commuter trains deep underground!
Odenplan and the main commuter train station called Stockholm City. This station is located under the main subway station T-Centralen, which in turn is under the Central Train Station. It is over 40 meters under street level and the station includes 44 new escalators and 17 elevators. When transferring from trains/subways to commuter trains, just follow the signs for Pendeltåg or Commuter Rail.
Nynäshamn for the ferry to Gotland, to the new Friends Arena (concerts, sporting events), the new giant shopping center Mall of Scandinavia, to Barkarby for some outlet shopping, the international fairgrounds at Älvsjö (conventions/fairs), a day trip to the city of Uppsala and, more importantly, the Arlanda airport.
the world's longest art gallery. I visited the Stockholm City station yesterday and it was fun just to walk around. Though I would avoid doing this during rush hour! For guests of the Rival Hotel, you can easily catch a commuter train at the nearby Stockholm Södra Station (no changes there). This station is located just four blocks from the hotel.