1970年(nian)(nian),懷德縣(xian)文化部門對境內(nei)的遺址進行了(le)(le)全面的普查,在(zai)城(cheng)址內(nei)采集(ji)、征集(ji)各類文物數十件。1983、2009年(nian)(nian),通過第二次、第三次全國文物普查,對城(cheng)址進行了(le)(le)系統的調查和(he)著錄。
五家子城址周(zhou)長近3000米,具有州(zhou)治規模,可能為遼(liao)信州(zhou)下轄之州(zhou)、縣城。
城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)址分為(wei)內(nei)、外(wai)(wai)二城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng),城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)垣(yuan)均夯(hang)土構筑。外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)大致呈南(nan)(nan)北(bei)向的長(chang)方形(xing)(xing),東(dong)、西(xi)兩墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)(yue)823米(mi)(mi)(mi),南(nan)(nan)、北(bei)兩墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)(yue)609.5米(mi)(mi)(mi),周長(chang)約(yue)(yue)(yue)2865米(mi)(mi)(mi)。外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)殘(can)損嚴重,城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)垣(yuan)基(ji)本無存(cun),是否存(cun)有馬面(mian)、甕(weng)門等遺(yi)跡(ji)(ji)(ji)已不(bu)得而(er)知。外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)四(si)角建(jian)有角樓(lou)(lou)(lou),東(dong)北(bei)角樓(lou)(lou)(lou)現存(cun)好,平(ping)面(mian)近圓(yuan)形(xing)(xing),直(zhi)徑(jing)約(yue)(yue)(yue)12米(mi)(mi)(mi),殘(can)高約(yue)(yue)(yue)2米(mi)(mi)(mi),其余(yu)3處(chu)角樓(lou)(lou)(lou)地表僅見稍高于(yu)地表的殘(can)跡(ji)(ji)(ji)。外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)墻(qiang)(qiang)(qiang)位置,距內(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)南(nan)(nan)墻(qiang)(qiang)(qiang)約(yue)(yue)(yue)30米(mi)(mi)(mi)處(chu),現存(cun)一高約(yue)(yue)(yue)6米(mi)(mi)(mi)的圓(yuan)形(xing)(xing)臺(tai)基(ji),疑為(wei)外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)墻(qiang)(qiang)(qiang)甕(weng)門的殘(can)跡(ji)(ji)(ji)。城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)外(wai)(wai)10米(mi)(mi)(mi)處(chu),東(dong)、西(xi)、北(bei)三面(mian)可見護城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)壕(hao)(hao)遺(yi)跡(ji)(ji)(ji),唯東(dong)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)不(bu)見城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)壕(hao)(hao)跡(ji)(ji)(ji)象,內(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)位于(yu)外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)的東(dong)北(bei)角,東(dong)、北(bei)兩墻(qiang)(qiang)(qiang)借用外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)的東(dong)、北(bei)二墻(qiang)(qiang)(qiang),另筑西(xi)墻(qiang)(qiang)(qiang)和南(nan)(nan)墻(qiang)(qiang)(qiang)而(er)成。內(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)平(ping)面(mian)近正方形(xing)(xing),東(dong)、西(xi)兩墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)(yue)341米(mi)(mi)(mi),南(nan)(nan)、北(bei)兩墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)(yue)320.5米(mi)(mi)(mi),周長(chang)約(yue)(yue)(yue)1323米(mi)(mi)(mi)。其中南(nan)(nan)墻(qiang)(qiang)(qiang)保存(cun)好,基(ji)寬(kuan)(kuan)約(yue)(yue)(yue)8米(mi)(mi)(mi),現高5~6米(mi)(mi)(mi),其余(yu)3面(mian)墻(qiang)(qiang)(qiang)體地表多僅存(cun)殘(can)跡(ji)(ji)(ji)。內(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)四(si)角構筑有角樓(lou)(lou)(lou),東(dong)北(bei)角樓(lou)(lou)(lou)即為(wei)外(wai)(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)北(bei)角樓(lou)(lou)(lou)。現存(cun)東(dong)南(nan)(nan)、西(xi)南(nan)(nan)角樓(lou)(lou)(lou),尤以東(dong)南(nan)(nan)角樓(lou)(lou)(lou)較為(wei)完整,平(ping)面(mian)近圓(yuan)形(xing)(xing),基(ji)寬(kuan)(kuan)約(yue)(yue)(yue)16米(mi)(mi)(mi),高約(yue)(yue)(yue)8米(mi)(mi)(mi)。內(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)未見門址與甕(weng)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)遺(yi)跡(ji)(ji)(ji)。
外(wai)城(cheng)(cheng)地表遺(yi)物(wu)豐(feng)富,尤以(yi)(yi)(yi)外(wai)城(cheng)(cheng)南側近河一(yi)帶(dai)遺(yi)物(wu)更為(wei)豐(feng)富。內城(cheng)(cheng)遺(yi)物(wu)則(ze)非(fei)常零星,僅見(jian)少(shao)量細泥(ni)質灰(hui)陶(tao)片(pian)和(he)白(bai)瓷(ci)片(pian),以(yi)(yi)(yi)及青磚和(he)布紋(wen)瓦殘(can)片(pian)。外(wai)城(cheng)(cheng)遺(yi)物(wu)以(yi)(yi)(yi)陶(tao)、瓷(ci)器(qi)(qi)為(wei)主(zhu)。陶(tao)器(qi)(qi)以(yi)(yi)(yi)泥(ni)質灰(hui)陶(tao)為(wei)主(zhu),均(jun)(jun)輪制,火候較(jiao)(jiao)高、陶(tao)質堅硬。器(qi)(qi)形包括罐、甕(weng)、盆、壺(hu)等。陶(tao)器(qi)(qi)紋(wen)飾多(duo)(duo)樣,以(yi)(yi)(yi)多(duo)(duo)種形式(shi)的(de)附加堆紋(wen)為(wei)主(zhu),還可見(jian)篦齒(chi)紋(wen)、卷云紋(wen)等。另有少(shao)量的(de)夾砂陶(tao),主(zhu)要(yao)出于城(cheng)(cheng)外(wai)南側,器(qi)(qi)形多(duo)(duo)較(jiao)(jiao)小,可能為(wei)青銅時代遺(yi)物(wu)。城(cheng)(cheng)內出土瓷(ci)器(qi)(qi)均(jun)(jun)為(wei)白(bai)瓷(ci),胎(tai)質粗糙(cao),釉色(se)泛黃,器(qi)(qi)形有碗(wan)、盤、碟等。
城(cheng)(cheng)(cheng)址(zhi)雖未發掘(jue),城(cheng)(cheng)(cheng)址(zhi)的(de)年(nian)代、性質認定尚無(wu)充分證據(ju),但城(cheng)(cheng)(cheng)內(nei)出土遺(yi)物的(de)特(te)點表面,遺(yi)物多為遼(liao)金時期。《遼(liao)史》信(xin)州(zhou)條下(xia)記錄信(xin)州(zhou)轄(xia)(xia)三州(zhou)、二縣。五家子城(cheng)(cheng)(cheng)址(zhi)周(zhou)長(chang)近3000米(mi),具(ju)(ju)有(you)州(zhou)治(zhi)(zhi)規模,可(ke)能(neng)為遼(liao)信(xin)州(zhou)下(xia)轄(xia)(xia)之州(zhou)、縣城(cheng)(cheng)(cheng)。對研究當(dang)時的(de)政(zheng)治(zhi)(zhi)、經濟、軍事、文化、交通(tong)等各(ge)方面都具(ju)(ju)有(you)較高的(de)歷史價值(zhi)。