Located on top of Hellenstein Mountain and overlooking the city, the most important building and landmark of Heidenheim is Hellenstein Castle.
Notable structures in the inner city are: Protestant Michaels' Church (former parish seat of the city), the Elmar-Doch-House, the Crown Inn and Pub, the Lower Gate, Villa Waldemaier, the burgher tower Turmle, the Castle Pharmacy, the weavers' settlement, the Heathland Smithy, the Old Mint and old Peters' Church (today cemetery chapel).
The construction facility for the manufacture of large turbines built for the local Voith company in 1924 is a significant industrial historic landmark.
The little castle in Schnaitheim is situated at the Brenz river's edge and offers a sight to see for visitors and residents alike. The Schnaitheim Mill is located just a few hundred yards away with its large wheel though operation of the mill was halted several years ago.
In Mergelstetten the old church was torn down in 1841 and replaced with a new, Protestant church built in neo-gothic style. The building was commissioned by Carl Alexander Heideloff who also commissioned Lichtenstein Castle. Lumber was used to build parts of the church because the parish was poor at the time. For the same reason the church tower wasn't built as tall as originally planned. Nonetheless, this church is popular and picturesque and frequently used on postcards.
Every other year the Shepherd Run takes place in Heidenheim, first held in 1723 by Duke Eberhard Ludwig. It attracts all the shepherds in the area. Part of the Shepherd Run festivities is the crowning of a new shepherd king and queen. The Run was held until 1828. After that followed a long break until 1922 when it was held again (five times until 1952). Since 1972 it is once again an integral part of Heidenheim's regular cultural program.
In 2006 Heidenheim hosted the bi-annual Baden-Wurttemberg State Botanical Show. Heidenheim annually hosts a World Cup fencing tournament in epee. Because of the size and depth of the field, the Heidenheim event is considered the strongest epee event in the world, stronger even than the World Championships or the Olympic Games.
'''Opera Festival'''
Annually Heidenheim puts on the Opera Festival "Opernfestspiele Heidenheim" in Hellenstein Castle. The festival developed out of the former serenades held there. Over the past years it has received international recognition and critical acclaim under the artistic direction of conductor Marco-Maria Canonica. In the summer of 2009 the Festival will stage Marschner's opera "Der Vampyr", which will be the second part of a cycle of three operas under the motto "Romantik im Rittersaal". The first part was von Weber's "Der Freischutz", performed in 2008, and the third and final installment will be Wagner's "Der fliegende Hollander" in 2010. During the summer of 2010 all three operas will be performed in full cycles. The Opernfestspiele Heidenheim draws visitors from around Europe and overseas, and has significally boosted the city's reputation as an important cultural site. Residents also enjoy the annual theater festival in the outdoor Nature Theater.