2 links
LacusCurtius: Roman Fountains
penelope.uchicago.edu
Article from William Smith's Dictionary of Greek and Roman Antiquities (1875), illustrated with three woodcuts.
The Early Christian Baptisteries of Rome
spazioinwind.libero.it
The Swedish Institute of Classical Studies in Rome provides an illustrated introduction to the type and its function, and information on the remains of a baptistery belonging to th…