Early Christian churches
In the 4th century, once Christianity had the support of the state, its fast-growing congregations needed buildings far larger than the discreet meeting places, often in private houses, that they had used until then. Pagan temples were no model: their worship took place outdoors, with the temple as a windowless backdrop. Builders turned instead to the basilica, the Roman hall: a long nave with an aisle on each side, an apse at the far end opposite the main door, and a raised platform for the altar. Windows high in the walls let in daylight, which has stayed a mark of Christian churches ever since.
The churches in this atlas belong to that late Roman world. The Euphrasian Basilica in Poreč, a cathedral of the 6th century on the UNESCO list, is famous for the gold-ground mosaics of its apse. In Plovdiv the Small Basilica of the 5th century has its floor mosaics back in place, and near Perushtitsa the Red Church, a late Roman basilica of red brick, still stands about 14 m high. Under St. Pierre Cathedral in Geneva are the remains of the churches that came before it, the oldest from the end of the 4th century. Others stand inside late Roman forts and refuges, such as Tonovcov grad above the Soča, whose villagers had four churches. Each entry says what is left and how you get in.
Sources: Wikipedia (en) — Early Christian art and architecture; Wikipedia (en) — Euphrasian Basilica; Wikipedia (en) — Small Basilica, Plovdiv; Wikipedia (en) — Red Church (Bulgaria); Geneva Tourism — Site archéologique de la cathédrale Saint-Pierre; Tolminski muzej — Tonovcov grad
Albania
- Byllis
Roman city · Fier County · 1st c. BC – 6th c. AD
Bulgaria
- Red Church, Perushtitsa
Roman church · Plovdiv Province · 5th – 7th c. AD
- Small Basilica of Philippopolis
Roman church · Plovdiv Province · 5th – 6th c. AD
Croatia
- Euphrasian Basilica
Roman church · Istria County · 4th – 6th c. AD
Greece
- Church of the Acheiropoietos
Roman church · Thessaloniki · 5th – 7th c. AD
- Dion
Roman city · Pieria · 1st c. BC – 5th c. AD
- Gortyn
Roman city · Heraklion · 1st c. BC – 7th c. AD
- Hagia Sophia, Thessaloniki
Roman church · Thessaloniki · 6th – 7th c. AD
- Lissos
Roman site · Chania · 1st c. BC – 7th c. AD
- Messene
Roman site · Messenia · 1st c. BC – 4th c. AD
- Nicopolis
Roman city · Preveza · 1st c. BC – 7th c. AD
- Philippi
Roman city · Kavala · 1st c. BC – 7th c. AD
- Roman Villa of Skala
Roman villa · Kefallonia · 1st – 7th c. AD
Italy
- Akragas/Agrigentum
Roman city · Sicily · 6th c. BC – 7th c. AD
- Albingaunum – Albenga
Roman city · Liguria · 2nd c. BC – 6th c. AD
- Aquileia
Roman city · Friuli-Venezia Giulia · 2nd c. BC – 7th c. AD
- Archaeological area of the Vicenza cathedral
Roman town house · Veneto · 1st c. BC – 4th c. AD
- Archbishop's Chapel, Ravenna
Roman church · Emilia-Romagna · 5th – 6th c. AD
- Baptistry of Neon
Roman baptistery · Emilia-Romagna · 5th – 7th c. AD
- Basilica of Saint Lawrence outside the Walls
Roman church · Lazio · 4th – 7th c. AD
- Basilica of Saint Paul outside the Walls
Roman church · Lazio · 4th – 7th c. AD
- Basilica of San Vitale
Roman church · Emilia-Romagna · 6th – 7th c. AD
- Basilica of Sant'Apollinare in Classe
Roman church · Emilia-Romagna · 6th – 7th c. AD
- Catacombs in Syracuse
Roman necropolis · Sicily · 4th – 6th c. AD
- Catacombs of San Gennaro
Roman necropolis · Campania · 2nd – 6th c. AD
- Cava d’Ispica
Roman necropolis · Sicily · 3rd – 7th c. AD
- Ipogeo di Santa Maria in Stelle
Roman site · Veneto · 3rd – 6th c. AD
- Macellum of Naples
Roman forum · Campania · 5th c. BC – 6th c. AD
- Milan amphitheatre
Roman amphitheatre · Lombardy · 1st – 6th c. AD
- Pantheon
Roman temple · Lazio · 1st c. BC – 7th c. AD
- Roman Forum
Roman forum · Lazio · 8th c. BC – 7th c. AD
- Roman houses of the Caelian
Roman site · Lazio · 2nd – 4th c. AD
- San Clemente Mithraeum
Roman temple · Lazio · 1st – 4th c. AD
- San Crisogono
Roman church · Lazio · 1st – 7th c. AD
- San Sebastiano fuori le mura
Roman necropolis · Lazio · 1st – 7th c. AD
- Santa Costanza
Roman tomb · Lazio · 4th – 7th c. AD
- Santa Pudenziana
Roman church · Lazio · 1st – 7th c. AD
- St John Lateran
Roman church · Lazio · 2nd – 5th c. AD
- Terme della Rotonda
Roman bath · Sicily · 1st – 6th c. AD
- Tombs of Via Latina
Roman necropolis · Lazio · 1st c. BC – 7th c. AD
- Trident(i)um – Trento
Roman city · Trentino-Alto Adige/Südtirol · 1st c. BC – 7th c. AD
- Villa Gordiani
Roman villa · Lazio · 1st c. BC – 7th c. AD
Slovenia
- Ajdna
Roman fort · Žirovnica · 4th – 6th c. AD
- Tonovcov grad
Roman fort · Kobarid · 3rd – 6th c. AD
Switzerland
- Archaeological site of St. Pierre Cathedral, Geneva
Roman church · Geneva · 4th – 7th c. AD
- Kirchlibuck fort, Bad Zurzach
Roman fort · Zurzach District, Aargau · 3rd – 5th c. AD