The Seekirchl – also known as the Heiligkreuzkirche – is the most famous landmark of Seefeld. It houses an old cross, the history of which dates back to the year 1628. Originally, the baroque Seekirchl stood amidst the Kreuzsee, artificially created by Duke Sigismund the Coinrich in the 15th century, which was drained again around 300 years later in 1808.

 It is reported that the following events led to the construction of the baroque Seekirchl:

A repentant pilgrim named Barbara Haißjackin obtained forgiveness for her sins through clear words from the cross before which she prayed. The woman felt comforted and reported the miracle to the cleric. One day, when Archduke Leopold V. passed by the miraculous cross, he was so moved by its sight that he requested a priest for confession and vowed to build a chapel for this crucifix. He fulfilled his vow in the year 1628 with the construction of the Seekirchl. The two events are depicted in the wall frescoes on the right and left. However, the chapel was not consecrated until the year 1666, a full 38 years later.

Particularly noteworthy is the octagonal floor plan of