The town, first mentioned in 902, grew up by the castle ( Babenberch ) which gave its name to the Babenberg family.

The Babenberg family rules Austria until 1246.

The Babenberg family tree of Stift Klosterneuburg

In 976 Leopold I, a member of the Babenberg family, who was a count in the Donnegau, is described as count of the Eastern March, a district not more than 60 miles in breadth on the eastern frontier of Bavaria which grew into the duchy of Austria.

With the death of Ottokar the first line of rulers of Styria became extinct ; the region fell successively to the Babenberg family, rulers of Austria, as stipulated in the Georgenberg Pact ; after their extinction to the control of Hungary ( 1254 – 60 ); to King Ottokar of Bohemia ; in 1276 to the Habsburgs, who provided it with Habsburgs for Styrian dukes during the years 1379-1439 and 1564-1619.

It possesses a church, in Romanesque style, dating from the 11th century, with fine cloisters and the tombs of several members of the Babenberg family.

The Babenberg family colors developed to the coat of arms of their Austrian possessions.

Heiligenkreuz was richly endowed by the founder's family, the Babenberg dynasty, and was active in the foundation of many daughter-houses.

A replacement had to be found for the Babenberg family, namely the Privilegium Minus, by which Austria was elevated to a duchy and gained complete independence from Bavaria.

* Frederick I of Austria ( Babenberg ) of the Babenberg family, 1195 – 1199

He was the son of Margrave Leopold I from the Babenberg family.

Frederick I of Austria ( c. 1175 – April 16, 1198 ) was a Duke of Austria from the Babenberg family.

It was assigned to the Babenberg family in 976.

He assisted the Franconian family of the Conradines in its feud with the Babenbergs for supremacy in Franconia ; after the battle of Fritzlar in 906 between the Babenbergs and Conradines he arranged for the capture and execution of Adalbert, count of Babenberg, breaking his promise of safe conduct.

He was the son of Margrave Ottokar II of Styria and Elisabeth of Austria from the Babenberg family.

In 976, the Margraviate of Ostarrîchi was given to the Babenberg family.

However, one condition was imposed by the nobles: Ottokar only can take the control over Austria and Styria if he married one of the Babenberg heiresses.

At that time, the Babenberg Dukes came to be one of the most influential ruling families in the region, peaking in the reign of Leopold VI ( 1198 – 1230 ).

It was not until the children of Albert I of Germany that the Babenberg blood was brought into the Habsburg line, though this blood was from the pre-ducal Babenbergs.

When Ottokar II married Gertrude's aunt, Margaret of Babenberg and moved into Austria, he had to flee, at first to Styria and later to the Sponheim court in Carinthia.

After their victories over European Knights at Legnica and Muhi, Mongol armies quickly advanced across Bohemia, Serbia, Babenberg Austria and into the Holy Roman Empire, but before Batu's forces could continue into Vienna and northern Albania, news of Ogedei's death in December 1241 brought a halt to the invasion.

Rapoto's II descendants however soon entered into fierce conflicts with the neighbouring Bishops of Passau and also with the mighty Austrian House of Babenberg.

Leader of the Styrian nobility, Ulrich had a hand in absorbing the duchy into the possessions of Rudolph of Habsburg after the ducal House of Babenberg had become extinct in 1246.

Conrad the Elder was killed, as had been two of the three Babenberg brothers ; however, the King Louis took the Conradines ' side and the third brother Adalbert of Babenberg was arrested and executed shortly thereafter, despite a promise of safe conduct by the king's chancellor Archbishop Hatto I of Mainz.

The city is very attractively situated, with two rivers the Steyr and the Enns flowing through it and meeting near the town centre in the shadow of the Babenberg castle " Lamberg " and the church of St. Michael.

Because the Babenberg Austria was inheritable by female lines, two rival candidates emerged after the last male Babenberg Frederick II, Duke of Austria, Styria and Carinthia died in 1246.

* House of Henneberg-Henneberg portion of Franconian Babenbergs and early Babenberg origins

As all of Hedwiga's brothers were killed in the Franconian Babenberg feud with the rivalling Conradines, Otto was able to adopt the strong position of his father-in-law and to evolve the united Saxon duchy under his rule.

The Conradines, counts in the Franconian Lahngau region, had been loyal supporters of the Carolingians ; they competed vigorously for predominance in Franconia with the sons of the Babenberg duke Henry of Franconia at Bamberg Castle.

Around 1125 Władysław married Agnes of Babenberg, daughter of Margrave Leopold III of Austria ; this union gave him a close connection with the Holy Roman Empire and the Kingdom of Germany: Agnes by her mother was a granddaughter of Emperor Henry IV and a half-sister of the Franconian duke Conrad III of Hohenstaufen, the later King of Germany.

1108 / 13 – d. 24 / 25 January 1163 ), was a German noblewoman, a scion of the Franconian House of Babenberg and by marriage High Duchess of Poland and Duchess of Silesia.

The leaders of the Babenbergs were the three sons of Duke Henry, who called themselves after their castle of Babenberg on the upper Main, around which their possessions centred.

While most of the Traungau fell to the Babenberg duchy of Austria upon the deposition of the Bavarian duke Henry the Lion in 1180, the southeastern Ausseerland remained with the newly established Duchy of Styria, which nevertheless from 1192 was held in personal union by the Austrian Babenbergs.

* Poppo ( Babenberg ) ( died 839 / 41 ), an early ninth-century ancestor of the Babenbergs

William of Montferrat ( early 1140s – 1177 ), also called William Longsword ( modern Italian Guglielmo Lungaspada ; original Occitan Guilhem Longa-Espia ), was the Count of Jaffa and Ascalon, the eldest son of William V, Marquess of Montferrat and Judith of Babenberg.

Leopold I ( died 994 ), also Luitpold or Liutpold, called the Illustrious ( der Erlauchte ), was the first Margrave of Austria from the House of Babenberg.

Leopold VI ( 1176 – 28 July 1230 ), called the Glorious, from the House of Babenberg, was Duke of Austria from 1198 to 1230 and of Styria from 1194 to 1230.

Also called the Georgenberg Compact, it has been called by English-speaking historians a " Styrian Magna Carta ", for it sought to guarantee the rights of the Styrian ministeriales in anticipation of the Babenberg acquisition.

Judith of Babenberg ( c. late 1110s / 1120 – after 1168 ), ( Jutta, sometimes called Julitta or Ita in Latin sources ), was a daughter of Agnes of Germany and her second husband Leopold III of Austria.

Conrad was the second son of Marquis William V of Montferrat, " the Elder ", and his wife Judith of Babenberg.

Conrad himself had risen to the position of duke of Franconia only after defeating the rival Babenberg counts in a battle near Fritzlar in 906, in which his father, Conrad, Duke of Thuringia the Elder, was killed.

While Louis the Blind, the King of Provence became King of Italy and even Emperor in 901, Louis the Child had to deal with the fierce feud between the Babenberg dynasty and Duke Conrad the Elder over the stem duchy of Franconia.