The "Spitalskapelle auf dem Martinsberge" is a flat-roofed sacral building with a semicircular choir and ridge turret. The three-axis quarry stone building dates from the 12th century. Many details refer to the Romanesque era. The former side aisles and hospital buildings have not survived.

The choir room is lit by one rectangular window in the north and one in the south. The choir room, which today is raised by 48 cm by means of three steps, is separated from the rectangular church room by a triumphal arch. The nave is about 11.5 meters long and 7 meters wide and has three Romanesque clerestory windows on the right and left, and two on the west wall. A baroque reconstruction could have taken place around 1708, since a papal indulgence document exists from that year. In 1854 the chapel fell into disrepair, and in 1890 only the remains of the walls were left.

The turret was only added when the roof was renewed in 1898. The Chapel of the Holy Spirit is mentioned for the first time in a letter of indulgence from 1332, issued in Avignon and now kept in the Lahnstein city archives. According to documents, a vicarage was already occupied before 1342. In 1505 a farm near the Holy Spirit Chapel (not the hospital) is sold. Also in 1575 the yard near the Holy Spirit Chapel is mentioned.

The chapel is located at a fresh water spring, which was said to have healing properties already in the 14th century, and at the old high road from Oberlahnstein to the Erzbach valley (mining since Roman times), Bad Ems and Nassau. Christian von Stramberg tells of the legend of the rich Regina Waibelung, who founded a leprosy hospital after lovesickness and also nursed the sick there herself.

When she herself fell ill, the spring sprang up after a prayer and she recovered after washing her hands. The healing spring was refurbished in 1972 with a natural granite basin and memorial plaque, and again in 2018. The last interior renovation was done in 2000 by the "Association for the Preservation and Renovation of Catholic Churches and Chapels of the Parish of St. Martin". Nothing has been preserved from the old furnishings of the chapel. Today the chapel is furnished in baroque style. The altar used to be in the Wenceslas Chapel.

Two altar paintings date from 1816 and used to hang in the parish church of St. Martin. The figures of the saints Wendelinus, King David and Sebastian are also baroque, while the neo-Gothic Mother of God is a replica of the Hallgarten Madonna made by Caspar Weis. A Way of the Cross once led up to the Chapel of the Holy Spirit, which was walked during Holy Week and is commemorated today by the street name "Auf'm Charweg". Older citizens can still remember the St. Mark's procession (April 25) and the petition processions on the three days before Ascension Day, which ended with a Holy Mass in the Holy Spirit Chapel.