You have a SharePoint Server 2010 Service Pack 1 (SP1) Web application that has the URL
http://portal.contoso.com. You have a site collection that has a top-level site named
http://portal.contoso.com. The site collection administrator deletes http://portal.contoso.com. You

need to restore only the http://portal.contoso.com site collection from the last backup of the farm.
What should you do first?

A.
Restore the hosting content database to a new location.

B.
Run the restore-spsite cmdlet.

C.
Restore the hosting Web application to the current Web application location.

D.
Run stsadm.exe and specify the -export option.

Explanation:
To do site restores the syntax is almost just as easy. You will need to use the same SharePoint 2010
Management Shell as doing the backup.
Restore-SPSite -Identity SiteCollectionURLHere -Path BackupFilePathHere [-DatabaseServer
DatabaseServerNameHere] [-DatabaseName ContentDatabaseNameHere] [-HostHeader
HostHeaderHere] [-
Force] [-GradualDelete] [-Verbose]
DatabaseServer – Specify the server for the content database
DatabaseName – Specify the name of the content database
HostHeader – URL of the Web application that will hold the host-named site collection
Force – Overwrite the site collection if it exists
GradualDelete – Recommended for site collections over 1 Gig in size, existing data is marked as
deleted and gradually removed over time by a job rather than all at once to reduce the performance
hit of deleting largeamounts of data
http://www.bradleyschacht.com/backup-and-restore-sharepoint-2010-site-collection-withpowershell/