Katarina kyrka, Högbergsgatan 13, +46 8 743 68 00 . Open to the public M-F 11AM-5PM, Sa-Su 10AM-5PM. Katarina kyrka ("Church of Catherine"), named after Princess Catherine, mother of King Charles X of Sweden, can be seen from many parts of central Stockholm from its location on a Södermalm hill. The church was built 1656–1695 and has been rebuilt twice after being destroyed by fires. After the first fire in 1723, the church was given a larger, octagonal tower. Following a new fire in May 1990 which left almost nothing but the external walls, the church was faithfully reconstructed and reopened in 1995. Several notable Swedes are buried in the cemetery. The most well-known is former Foreign Minister Anna Lindh, who was assassinated in 2003.
The northern parts of Södermalm offer some excellent viewpoints with panoramas of the central parts of the city:
Walking eastwards from Slussen up Katarinavägen you will reach the picturesque street Fjällgatan, with a view of Gamla Stan from the east.
Monteliusvägen, a walking path that you reach from Bastugatan (north of T Mariatorget) offers a similar view from the west. Benches and tables offer picnic possibilities.
Skinnarviksberget, a hill further west, close to the Zinkensdamm subway station, is a good option if you prefer cliffs to streets. When exiting the station turn back and head to the north. Walk up a small street to the right and climb the hill. Look for the "Kattenvägen" sign.
Transport Museum (Spårvägsmuseet), Tegelviksgatan 22 (Bus 2 from Slussen) . Open M-F 10AM-5PM, Sa-Su 11AM-4PM. Maybe not for everyone, but still entertaining, Spårvägsmuseet is a museum of Stockholm's public transportation. Walking through historical buses and subway cars is quite fun but not enough text is in English. Admission 30SEK (15SEK reduced price).
Between Slussen and Mariatorget, the Hornsgatan street has a narrow sett-paved side section on the north side, above the main street, nicknamed "Hornsgatspuckeln" ("the Hornsgatan bump") , with a lot of galleries. Some examples are the ceramics and glassware gallery blås & knåda (Hornsgatan 26, +46 8 642 77 67, ) Konsthantverkarna (Sodermalms torg 4, +46 8 611 03 70, ) and Grafiska Sällskapet ("The Swedish Printmakers' Association", Hornsgatan 6, +46 8 643 88 04, ).
The island Långholmen (T Hornstull) has several good spots for swimming, including a small sandy beach.