SharePoint 2013 - Accessing Root Subsites and getting list data

How do I get to Sites that are built off the main root site (http://sptest.domain.com/)

Then listed in the "Sites" folder in the SharePoint Connnections Tree?

http://sptest.domain.com/Department

Then there is a list I want the data from in the Department site.

First I am just trying to get the lists to display and it is not working.  Thanks for any tips.

private void FillProvidersDdl()
        {
            using(SPWeb web = new SPSite("http://sptest.domain.com/Departements"))
            {
                ddlProviderByName.DataSource = web.Lists["cb63967c-23f9-4257-9968-ac4dc6c1575e"];
                ddlProviderByName.DataTextField = "main";
                ddlProviderByName.DataBind();
                var lists = web.Lists;

                //from SPList list in web.Lists
                //where list.Hidden == false
                //select list;

                foreach (SPList list in lists)
                {
                    ltTest.Text = ("<br />" + list.Title);
                }
              }
        }

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