Among the priests of the clerical community of Kosd, who go to court in the case of the tithe against the bishop of Weißenburg together with other saxon deaneries in 1309, there is also mentioned Nikolaus of Jakobsdorf. This is the first written reference of the parish. At 1500 Jakobsdorf is registered in a list of the „Schenker Stuhl“ (today Cincu) as a free parish on the king’s ground with 75 landlords, one mill, one school, three poor people and two desert farms. At the time when the church castle was built it was a populous parish, what can also be seen from the extent of the ramparts. 

As the foundation of the village took place in the twelfth century, it is for sure that the stony gothic one-nave hall church built in the beginning of the fourteenth century had not been the first sacral building, but had been built on and with the remainders of an older church which assumedly perished during the Mongolian assault. The stylistic elements of the hall church are so rare that they do not offer any indication for a more accurate temporal classification. An unprofiled pointed triumphal arch separates the sanctuary from the hall which originally had the same width. The hall is covered by a tunnel vault with a simple rhombus pattern made of clay ribs, the sanctuary by a cross vault and the pentagonal eastern apse by a five ribbed tunnel vault, which appears very primitively due to its irregular and uneven masonry. A still existing stone threshold and two upright pillars on the outside southern wall of the sanctuary show that there once was the entry for the priests.  

This and the loftlike vault of the sanctuary square maintain the presumption that parts of an older church had been used for building the hall church. The sacristy vestibule in the northern wall of the sanctuary is formed by a simple stony pointed arch. The small tunnel vaulted sacristy has one little eastward window only. In the southeast wall of the apse a small acute-angledly closed sacramental niche is inserted. In the course of the current restoration the sacramental chapel of the eternal worship was rebuilt. Besides the later erected northern vestibule the hall undoubtedly had a western vestibule, too, which fell victim to the extension of the donjon at the western end of the hall. 

In the fifteenth century the armoring already began. The first step was the construction of the donjon at the western end of the hall. The walls are 3 meters thick at the basis, 9,40 metres long in square and reach a height of 26 meters. Among all donjons of the five neighbor villages the one of Iakobeni/Jakobsdorf is the highest one. From the beginning its southern front was in line with the front of the church, while the northern front of the broader tower protruded. That is why after the completion of the donjon the northern wall of the church was broken down and put off, so that now it connects the donjon corner with the sacristy wall resulting in a broadening of the northern half of the hall compared to the axis of symmetry. Thus the pointed arched entrance of the donjon in the middle of the western wall of the hall is not situated on the symmetry axis but shifted northwards. 

The oak door was densely studded with 10 cms broad iron strips and closes the entrance to the donjon, which has a windowless tunnel vaulted first floor. Close to the entrance on the right side opens up a stair gallery as broad as the wall, runs around the northeastern corner of the donjon and meets the northern wall of the second floor, which also is covered by a tunnel vault (later on it served for a pantry). The stair gallery which connects the second with the third floor leads up within the size of the eastern wall. Today there is a later constructed wooden staircase leading up from the inner ward to the third floor. This is also connected with the likewise later erected western gallery of the hall. Three arrow-slits open up on the forth as well as on the fifth floor. 

On the outside they are only 20 cms wide, inside they are 1,50 meters wide niches for the bowmen, which are covered with flagstones in the narrow part and with wooden beams in the broader one. The sixth and seventh floor, which tower up above the church roof, have four open arrow-slits each. They are not situated on a vertical axis on top of each other but staggered aside. The circular protruding battlement is planked with wood up to the gutter, carries a steep pyramidal roof and also holds the belfry. By the means of an iron lifting jack the bells were lifted from the battlement to the tower. They are three new bells of the twentieth century.  

The second step of the fortification works was the construction of a battlement floor above sactuary and nave. Its embracing walls, provided with arrow-slits, are situated 2 meters high on the so called defence arches, 17 brick arches, which – 40 cms advanced to the line of the church walls – draw from one to the next of 18 bows surrounding the building. Within the intervals between the two walls originated by that the loopholes or maschikulis open up, through which hot pitch, grease or boiling water was poured down on the enemies besetting the walls.  

In the northern wall of the battlement floor a door opens up. On its lintel a heavy duty role for the lifting of sacks and buckets is fixed. The erection of the battlement floor also caused the heightening of the rafters, the year 1602 is engraved in one of its beams. From the third floor of the donjon a door opens up to the battlement floor of the church – the brick bordering of this passage proves that it was broken through afterwards. The eastward arrow-slit of the forth donjon floor is hidden by the church roof – unmistakeable evidence for the fact that the battlement floor was only put on the church after the completion of the donjon. 

The third step of the fortification works began with the construction of the eastern tower above the sacristy – five battlement floors and one battlement planked with wood on top of them – which are connected with the huge battlement floor of the church. In order to fortify the foundation the northern wall of the sacristy was made twice as thick. At the basis the retaining wall is 3 meters thick. A buttress enclosed in the sacristy tower supplies evidence of its later erection as well as of the eastward attached defence arch – the lower part of its support column was removed because it hid the fire sector of one of the arrow-slits of the donjon. The entrance to the sacristy tower is located in its western wall, on the second floor, only accessible by a mobile ladder. Inside the tower the floors which are separated from each other by wooden platforms are connected by block stairs.

From the fourth floor you enter the church attic – thus all three fortifications of this elaborate defense church were connected and aligned to the particularly menaced sides of the castle. Another proof that the sacristy tower was the last erected part of the fortification is the fact that the part of the tower protruding into the attic remained raw – if it had been built before the battlement floor of the church, it had overtopped the roof and would have been plastered.

The north portal of the hall got a small portico in the 19th century; between the two western buttresses of the north front a covered staircase was incorporated. In order to increase the number of seats in the church the galleries supported by wooden col-umns and scaffoldings – “laterium”, saxon “Glater” – were placed at the northern, southern and western walls of the hall in 1784 and broadened already in 1805. It is interesting that by addition of seat rows on the galleries (there are two on the south-ern, three on the northern and even five on the western) the front balustrades were renovated and the old panels placed at the rearwards adjacent benches – so that here the style history of gallery painting can be watched.

Being almost square the circular wall encloses a narrow courtyard – only in the east the curtain wall shows a curve supported by buttresses against the scarp. The main entrance in the north front is guarded by a gate tower with a portcullis, the hook stones of which are still sticking out beside the entrance. At the northern side, where the circular wall follows the scarp, another almost semicircular polygonal front court was added later on, in the north protected by a bastion, which today is the warden’s house. The northwest corner of the inner circle protects a protruding, well-fortified constructed fruit house. The wall tower protruding from the southeast corner has been removed, on the other hand the three-floor tower house in the southwest corner is still existing. It stands on the most protected place, as there was no danger from the inclining mountain plateau in the south. Its ground floor is a barrel vault, in the north front towards the courtyard three entrances with wooden doors open up on top of each other. The reveal of one small window in the north wall is painted red, brown and black in form of a triangle; even the tower edges bear traces of paintings. The second and third floor have a common ventiduct, the construction of which disproves the assumption it could have been a privy or a chimney as in the other tower houses. Eastern and northern side of the inner circular wall are equipped with special arrow slits, the oak frame of which are barred with a wooden, on a metal spindle turnable bolt, which can be opened from inside only, so that two gun barrels could be put through. Except for the east wall of the front court the castle complex is very well pre-served, the fortified church with its ornamental moulding of the defense arches, the vertical division of its fronts by the buttresses and the tower roofs protruding each other is of particular beauty and expressiveness.