How to make use of Ruins?

[Extraordinarily Mature Slav]

I saw in a tutorial that I ruins are very valuable yet I don't know how to use them. They have an extremely high amount of scavenge points. But I don't know what that means and how to use these "scavenge points".
Edit: I just saw the recycling facility so nevermind. But are there other uses for ruins?

[Thomas]

You can have 'archaeological' digs in ruins (discover via card on existing ruins or naturally (?)) It will show as silver/gold pyramides on map - and then as an extra you will receive machines/hi-tech/blue(rare) cards from recycling facility.

[maerchen]

If you happen to stumble upon a megacity ruin, exploit that. Adjacent ruin hexes give a bonus to recyclers. 5.5.2.4, page 199 manual.

[MightyPsychoBat]

Ruins also make for powerful defensive bonus too. Tanks/Vehicles and artillery are far less effective when handling entrenched infantry(ESPECIALLY machine gunners) in ruins, however walkers recive no penatlys so they make for useful armoured bonus buffs when on the offensive.
*pro tip, build cities inside ruins and the terrain bonus still works. This also applies to the enemy, as some of their cities may spawn in a single hex ruin.

[Enoukdep Mav]

Originally posted by MightyPsychoBat:

Ruins also make for powerful defensive bonus too. Tanks/Vehicles and artillery are far less effective when handling entrenched infantry(ESPECIALLY machine gunners) in ruins, however walkers recive no penatlys so they make for useful armoured bonus buffs when on the offensive.
*pro tip, build cities inside ruins and the terrain bonus still works. This also applies to the enemy, as some of their cities may spawn in a single hex ruin.

...That explains this one fight I was in in one of my early games; an all but invincible city. I was camped outside it for so long that I eventually managed to take it after researching and inventing 4-hex radius tactical aircraft and building airfields right outside it.

[maerchen]

Get the recon up to 400 via probing attacks with The Expendables aka Militia, then attack with your premium units in force. Sieges will only take 1-3 turns when you do this with well supplied units.
If that city was of a major regime, it could have had superior tech, then a siege can indeed last forever.
Interesting that you were able to take that city that way, Dunkirk fulfilled.