This is a long sentence. It has five clauses:
A few minutes later we had reached the lodge-gates, a maze of fantastic tracery in wrought iron, with weather-bitten pillars on either side, blotched with lichens, and surmounted by the boars' heads of the Baskervilles.
Another way to look at it is like this:
A few minutes later we had reached the lodge-gates, a maze of fantastic tracery in wrought iron, with weather-bitten pillars on either side, blotched with lichens, and surmounted by the boars' heads of the Baskervilles.
We reached the gates, now let me spend four clauses telling you all about them.
Why spend so long describing a pair of gates?
Let’s rewrite this snippet in the simplest way possible.