Can I sync a lead web history (the list of the url he was visiting) from Marketo to SFDC, and how?
This is already visible in SalesInsight. And there is not much of a possibility to do it elsewhere as you cannot populate a SFDC custom object from Marketo.
You could develop a complex scenario using webhooks or API's, but is it really worth it?
You would not be able to physically move the data into Salesforce without using the API. Also, there would be a lot of data, which would eat into the relatively low object data limits in Salesforce.