A second period of study at Göttingen followed, along with (between 1806 and 1808) time at a gallery at Dresden.
 In autumn 1808, he set out on a second Italian trip, this time accompanied by Ernst Heinrich Tölken.
 On their way to Italy, they encountered Jean Paul in Bayreuth and visited the gallery at Schleissheim Palace near Munich.
 They reached Rome in 1809 and there met and became friends with the archaeologist and art historian Carl Haller von Hallerstein, the Danish archaeologists and philologists Peter Oluf Brondsted and Georg Koës, the German painter Jakob Linckh, and the then Austrian consul in Greece George Christian Gropius.
 Bröndsted and Koës persuaded Stackelberg to accompany them on their trip to Greece.
They intended to produce an archaeological publication upon their return, for which Stackelberg would produce landscapes.

The trip to Greece was long and adventurous, setting out from Naples in July 1810 and not arriving in the Piraeus until September.
 At Athens, they were joined by the British architects and archaeologists John Foster and Charles Robert Cockerell.
 The group carried out excavations at several Greek sites – in 1811 at the Temple of Aphaia at Aegina, they removed the fallen fragmentary pediment sculptures and on von Hallerstein's recommendation shipped them abroad and sold them the following year to Crown Prince Ludwig of Bavaria; and in 1812 they exposed parts of the temple of Apollo at Bassae (the frieze they found on it is now in the British Museum) and Aeacus's temple of Zeus Panhellenios (Panhellenic Zeus), again at Aegina.
A second period of study at Göttingen followed, along with (between 1806 and 1808) time at a gallery at Dresden.  In autumn 1808, he set out on a second Italian trip, this time accompanied by Ernst Heinrich Tölken.  On their way to Italy, they encountered Jean Paul in Bayreuth and visited the gallery at Schleissheim Palace near Munich.  They reached Rome in 1809 and there met and became friends with the archaeologist and art historian Carl Haller von Hallerstein, the Danish archaeologists and philologists Peter Oluf Brondsted and Georg Koës, the German painter Jakob Linckh, and the then Austrian consul in Greece George Christian Gropius.  Bröndsted and Koës persuaded Stackelberg to accompany them on their trip to Greece. They intended to produce an archaeological publication upon their return, for which Stackelberg would produce landscapes.
The trip to Greece was long and adventurous, setting out from Naples in July 1810 and not arriving in the Piraeus until September.  At Athens, they were joined by the British architects and archaeologists John Foster and Charles Robert Cockerell.  The group carried out excavations at several Greek sites – in 1811 at the Temple of Aphaia at Aegina, they removed the fallen fragmentary pediment sculptures and on von Hallerstein's recommendation shipped them abroad and sold them the following year to Crown Prince Ludwig of Bavaria; and in 1812 they exposed parts of the temple of Apollo at Bassae (the frieze they found on it is now in the British Museum) and Aeacus's temple of Zeus Panhellenios (Panhellenic Zeus), again at Aegina.
Otto Magnus von Stackelberg (archaeologist)