High at the head a branching olive grows
And crowns the pointed cliffs with shady boughs.
A cavern pleasant, though involved in night,
Beneath it lies, the Naiades delight:
Where bowls and urns of workmanship divine
And massy beams in native marble shine;
On which the Nymphs amazing webs display,
Of purple hue and exquisite array,
The busy bees within the urns secure
Honey delicious, and like nectar pure.
Perpetual waters through the grotto glide,
A lofty gate unfolds on either side;
That to the north is pervious to mankind:
The sacred south t'immortals is consign'd.
Homer, Odyssey, Pope tranls. (Book XIII, 122-135)
In Porphyry's short treatise De Antro Nympharum, he gives a symbolic interpretation of a brief, curious passage from Homer's Odyssey. The scene contains the following elements:
A cavern at the top of a cliff
An olive tree in front of it
Marble beams where Naiads weave purple garments
Bowls and urns filled with honey provided by bees
A stream of water flowing through
A North gate for mankind and a South gate for immortals
The Greek text is online:
Here's the Homeric passage from http://www.perseus.tufts.edu/hopper/
There is in the land of Ithaca a certain harbor of Phorcys, the old man of the sea, and at its mouth two projecting headlands sheer to seaward, but sloping down on the side toward the harbor. These keep back the great waves raised by heavy winds  without, but within the benched ships lie unmoored when they have reached the point of anchorage. At the head of the harbor is a long-leafed olive tree, and near it a pleasant, shadowy cave sacred to the nymphs that are called Naiads.  Therein are mixing bowls and jars of stone, and there too the bees store honey. And in the cave are long looms of stone, at which the nymphs weave webs of purple dye, a wonder to behold; and therein are also ever-flowing springs. Two doors there are to the cave,  one toward the North Wind, by which men go down, but that toward the South Wind is sacred, nor do men enter thereby; it is the way of the immortals.
Φόρκυνος δέ τίς ἐστι λιμήν, ἁλίοιο γέροντος,
ἐν δήμῳ Ἰθάκης: δύο δὲ προβλῆτες ἐν αὐτῷ
ἀκταὶ ἀπορρῶγες, λιμένος ποτιπεπτηυῖαι,
αἵ τ᾽ ἀνέμων σκεπόωσι δυσαήων μέγα κῦμα
100ἔκτοθεν: ἔντοσθεν δέ τ᾽ ἄνευ δεσμοῖο μένουσι
νῆες ἐΰσσελμοι, ὅτ᾽ ἂν ὅρμου μέτρον ἵκωνται.
αὐτὰρ ἐπὶ κρατὸς λιμένος τανύφυλλος ἐλαίη,
ἀγχόθι δ᾽ αὐτῆς ἄντρον ἐπήρατον ἠεροειδές,
ἱρὸν νυμφάων αἱ νηϊάδες καλέονται.
105ἐν δὲ κρητῆρές τε καὶ ἀμφιφορῆες ἔασιν
λάϊνοι: ἔνθα δ᾽ ἔπειτα τιθαιβώσσουσι μέλισσαι.
ἐν δ᾽ ἱστοὶ λίθεοι περιμήκεες, ἔνθα τε νύμφαι
φάρε᾽ ὑφαίνουσιν ἁλιπόρφυρα, θαῦμα ἰδέσθαι:
ἐν δ᾽ ὕδατ᾽ ἀενάοντα. δύω δέ τέ οἱ θύραι εἰσίν,
110αἱ μὲν πρὸς Βορέαο καταιβαταὶ ἀνθρώποισιν,
αἱ δ᾽ αὖ πρὸς Νότου εἰσὶ θεώτεραι: οὐδέ τι κείνῃ
ἄνδρες ἐσέρχονται, ἀλλ᾽ ἀθανάτων ὁδός ἐστιν.