Tolmin stands on the southern rim of the Julian Alps and is the largest settlement in the Upper Soca Valley (Slovene: Zgornje Posocje), close to the border with Italy. It is located on a terrace above the confluence of the Soca and Tolminka rivers, positioned beneath steep mountainous valleys. The old town gave its name to the entire Tolmin area (Slovene: Tolminsko) as its economic, cultural and administrative centre.

The area is located in the historic Goriška region, itself part of the larger Slovene Littoral, about 41 km (25 mi) north of Nova Gorica and 87 km (54 mi) west of the Slovene capital Ljubljana. In the north, the road leads further up the Soca River to Bovec, with an eastern branch-off to Škofja Loka and Idrija.

Main sights include:

• Tolmin's main sights are its old town centre, a modern sports park, and thousand-year-old castle ruins at the hill known as Kozlov rob.
• The area is home to a multitude of vestiges from World War I. The most significant relic of the time is the Javorca Church, dedicated to the Holy Spirit built above the Polog shepherds outpost in the Tolminka Valley by Austro-Hungarian soldiers to commemorate their deceased comrades.
• The museum, library, schools, and the town's open spaces provide venues for a variety of events, exhibitions, and presentations all year round. The Tolmin region is also a popular destination for artists from Slovenia and abroad.
• The parish church in the town is dedicated to the Assumption of Mary and belongs to the Diocese of Koper.
• Tolmin is known for the "Metalcamp" festival since 2004, which since 2013 is called Metaldays, which every year attracts about 10,000 people from whole Europe and other parts of world. Other festivals held in Tolmin are Punk Rock Holiday and the Overjam reggae festival.