Comparing the two Pulpits of the Baptistery in Pisa and Cathedral in Siena.
The Pulpit in the Baptistery of Pisa was completed in 1260 and the Pulpit in Siena’s cathedral followed five years later and was eventually completed in 1268. Nicola Pisano was Pivotal in the sculpting of them both. However, Pisano’s son Giovanni, assisted him in the latter along with a possible relative of Alnorfo Di Cambio. As with most Pulpits, they have both been moved around in their respective locations. Furthermore, they both depict the conventional scenes of the life of Christ. Namely the Annunciation, the Adoration of the Magi, the Slaughter of the Innocents, the Crucifixion and the Last Judgement.
The earlier Pulpit (Fig. 2) was among the first to step away from what was typical for their form. It was built at a time when the Gothic style had been introduced by the Pisan Cardinal as a ‘fashionable’ style. You can see this in the ‘bushy capitals’ which are a supposed ’Gothic variation of the Corinthian capital’.
Furthermore, Pisano also incorporates classical elements into his work. This can be seen across both Pulpits, in Fig. 2 with the naked classical figure (believed to be Hercules) and in Fig. 1 with the naked bodies in the Last Judgement scene. Conversely, such influences are most notably found in the form of Roman Sarcophagi. In fact, in the ‘Adoration of the Magi’ scene, St. Mary is depicted with a temple above her head - this is identical to a depiction found on a sarcophagus in the Camposanto (Fig. 2). What is more, it is asserted by Fred Kleiner that if you were to alter the dimensions of the panels slightly, then they would have been akin in form to Roman Sarcophagi. This is all an allusion to Pisa as the ‘New Rome’ as they were reproducing exact replicas in some cases of classical sculpture. The historian Christopher Klenhenz puts it in the following terms:
‘This hexagonal Pulpit is decorated with scenes from the life of Christ that are characterized by classical forms; like the inscriptions on the face of the Cathedral, these forms connect the work to the popular theme of Pisa as new Rome’. 
However, while he did begin to use new elements he did also continue in Medieval tradition somewhat in that the bottom of the columns are supported by lions (there is one lion breastfeeding so we can only assume Pisano wanted to depict a lioness but did so wrongly as it has a mane). Their inclusion alongside new, innovative elements, could be because the lions were so symbolically important. Their importance derives from folklore that states a lion will breathe into the open mouths of his cubs and give them vision which is an allusion to Resurrection. This feature was also carried forward for the later Pulpit in Siena; (Fig.1) but in contrast to the earlier pulpit, the latter lioness is depicted correctly. This could be either testament to Pisano’s improvement as an artist or the involvement of others; Charles Norton asserts the former saying that the ‘Sienese pulpit shows the advance that Niccola had made in the six years since the Pisan pulpit was completed’.
Considering the two Pulpits had were made under the same man, and not even a decade apart, they are bound to be similar. However, I believe the new generation of artists (in the form of his son, Giovanni) meant that the style of the latter Pulpit in Siena was developing akin to Proto - Renaissance sculpture. It was evidently not completely what we consider ‘Renaissance’ today but the development is evident. In my opinion, the Sienese Pulpit bridged the difficulties Nicola had with space and depth with the almost ease at which Giovanni achieved those very elements in his Pulpit in the Cathedral at Pisa at the beginning of the 14th century.
 C. Mamiya, F. Kleiner, Gardner’s Art Through the Ages, Western Perspective, (Wadsworth Publishing Co Inc; 12th Revised Edition, 2005), 406.
 C. Klenhenz, Medieval Italy: An Encyclopedia: 002 The Routledge Encyclopaedias of the middle ages (Routledge, 2003), 906.
 C. Norton, Historical Studies of Church Building in the Middle Ages: Venice, Siena, Florence 1902 (Kessinger Publication, 2003), 132.