A hagioscope (from Gr. άγιος, holy, and σκοπός, to see) or squint, in architecture, is an opening through the wall of a church in an oblique direction, to enable the worshippers in the transepts or other parts of the church, from which the altar was not visible, to see the elevation of the Host.
Hagioscopes were also sometimes known as "leper windows" wherein a squint was made in an external wall so that lepers and other non-desirables could see the service without coming into contact with the rest of the populace.
In medieval architecture Hagioscopes were often a low window in the chancel wall and were frequently protected by either a wooden shutter or iron bars. Hagioscopes are found on one or both sides of the chancel arch; in some cases a series of openings has been cut in the walls in an oblique line to enable a person standing in the porch (as in Bridgwater church, Somerset) to see the altar; in this case and in other instances such openings were sometimes provided for an attendant, who had to ring the Sanctus bell when the Host was elevated.
Sometimes squints were placed to enable nuns to observe the services - without having to give up their isolation. At the church of St Helen's in Bishopsgate, London, which is one of the largest surviving ancient churches of London, its interesting design arose from it once having been two separate places of worship. The first was a 13th-century parish church and the second was the chapel of a Benedictine convent.
Here on the convent side of the church we can find an ancient "squint", which allowed the nuns to observe the parish masses; church records show that the squint in this case was not enough for the nuns who were eventually admonished to "abstain from kissing secular persons," a habit to which it seems they had become "too prone".
In Germany a number of hagioscopes still exist or were rediscovered in the 19th and 20th century. They are found mainly in Lower Saxony which had a small population in the Middle ages and only a few bigger cities. In cities lepers lived together in housing estates which often had their own chapels. In Georgsmarienhütte the hagioscope of church St. Johann which belonged to the former Benedictine convent Kloster Oesede, founded in the 12th Century and reconstructed in the early 1980s. Nearby in Bad Iburg a hagioscope was rediscovered at St. Clemens, church of former Benedictine monastery in the castle and monastery complex Schloss Iburg. Other hagioscopes in Lower Saxony are found in Bokelesch, Westoverledingen, Dornum, Midlum, Kirchwahlingen (Gemeinde Böhme) and Hankensbüttel.
In Northrhine-Westphalia St. Antonius-Kapelle in Gescher-Tungerloh-Capellen has a hagioscope. St. Antonius is used as Autobahn chapel at Bundesautobahn 31. Another hagioscope is found in St. Ulricus in Börninghausen. In Rhineland-Palatinate the church of St. Eligius-Hospital in Neuerburg has a hagioscope. In Baden-Württemberg there is a hagioscope in St. Peter und Paul, the Old Cemetery Church of Nusplingen.
In Sweden Bro Kyrka near Visby on Gotland has a cross shaped hagioscope. Other hagioscopes are at the church of Vreta Abbey near Linköping, Granhult Kyrka in Uppvidinge and Husaby Kyrka in Götene. The wooden church in Granhult (Småland) has a hagioscope which can be closed.
Churches in England with hagioscopes include: