1970年,懷德縣(xian)文(wen)化部門對境內的遺址進行了(le)(le)全(quan)面的普查,在城址內采(cai)集(ji)、征(zheng)集(ji)各類(lei)文(wen)物數(shu)十(shi)件(jian)。1983、2009年,通(tong)過第(di)二(er)次(ci)、第(di)三次(ci)全(quan)國文(wen)物普查,對城址進行了(le)(le)系統的調查和著錄。
五家(jia)子城(cheng)(cheng)址周長(chang)近3000米(mi),具有州治規(gui)模,可能為遼(liao)信州下轄之州、縣(xian)城(cheng)(cheng)。
城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)址分為(wei)(wei)內(nei)(nei)、外(wai)二(er)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng),城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)垣(yuan)均夯土(tu)構筑。外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)大致呈南(nan)(nan)(nan)北(bei)(bei)(bei)(bei)向的(de)(de)長(chang)(chang)方形(xing),東(dong)、西(xi)(xi)(xi)兩(liang)墻(qiang)(qiang)長(chang)(chang)約(yue)(yue)(yue)(yue)823米(mi)(mi)(mi)(mi),南(nan)(nan)(nan)、北(bei)(bei)(bei)(bei)兩(liang)墻(qiang)(qiang)長(chang)(chang)約(yue)(yue)(yue)(yue)609.5米(mi)(mi)(mi)(mi),周(zhou)長(chang)(chang)約(yue)(yue)(yue)(yue)2865米(mi)(mi)(mi)(mi)。外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)殘(can)損嚴重,城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)垣(yuan)基本無(wu)存(cun)(cun)(cun),是否存(cun)(cun)(cun)有馬面、甕(weng)門等遺(yi)跡(ji)(ji)(ji)(ji)(ji)已不得而知。外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)四(si)角(jiao)(jiao)(jiao)(jiao)建有角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou),東(dong)北(bei)(bei)(bei)(bei)角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou)現存(cun)(cun)(cun)好(hao),平(ping)面近(jin)(jin)圓(yuan)形(xing),直徑約(yue)(yue)(yue)(yue)12米(mi)(mi)(mi)(mi),殘(can)高約(yue)(yue)(yue)(yue)2米(mi)(mi)(mi)(mi),其(qi)余3處角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou)地(di)表僅見稍高于地(di)表的(de)(de)殘(can)跡(ji)(ji)(ji)(ji)(ji)。外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)墻(qiang)(qiang)位(wei)置(zhi),距內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)南(nan)(nan)(nan)墻(qiang)(qiang)約(yue)(yue)(yue)(yue)30米(mi)(mi)(mi)(mi)處,現存(cun)(cun)(cun)一高約(yue)(yue)(yue)(yue)6米(mi)(mi)(mi)(mi)的(de)(de)圓(yuan)形(xing)臺基,疑為(wei)(wei)外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)墻(qiang)(qiang)甕(weng)門的(de)(de)殘(can)跡(ji)(ji)(ji)(ji)(ji)。城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)外(wai)10米(mi)(mi)(mi)(mi)處,東(dong)、西(xi)(xi)(xi)、北(bei)(bei)(bei)(bei)三(san)面可見護城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)壕遺(yi)跡(ji)(ji)(ji)(ji)(ji),唯東(dong)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)不見城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)壕跡(ji)(ji)(ji)(ji)(ji)象,內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)位(wei)于外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)的(de)(de)東(dong)北(bei)(bei)(bei)(bei)角(jiao)(jiao)(jiao)(jiao),東(dong)、北(bei)(bei)(bei)(bei)兩(liang)墻(qiang)(qiang)借用(yong)外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)的(de)(de)東(dong)、北(bei)(bei)(bei)(bei)二(er)墻(qiang)(qiang),另筑西(xi)(xi)(xi)墻(qiang)(qiang)和南(nan)(nan)(nan)墻(qiang)(qiang)而成(cheng)。內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)平(ping)面近(jin)(jin)正方形(xing),東(dong)、西(xi)(xi)(xi)兩(liang)墻(qiang)(qiang)長(chang)(chang)約(yue)(yue)(yue)(yue)341米(mi)(mi)(mi)(mi),南(nan)(nan)(nan)、北(bei)(bei)(bei)(bei)兩(liang)墻(qiang)(qiang)長(chang)(chang)約(yue)(yue)(yue)(yue)320.5米(mi)(mi)(mi)(mi),周(zhou)長(chang)(chang)約(yue)(yue)(yue)(yue)1323米(mi)(mi)(mi)(mi)。其(qi)中南(nan)(nan)(nan)墻(qiang)(qiang)保存(cun)(cun)(cun)好(hao),基寬(kuan)約(yue)(yue)(yue)(yue)8米(mi)(mi)(mi)(mi),現高5~6米(mi)(mi)(mi)(mi),其(qi)余3面墻(qiang)(qiang)體地(di)表多僅存(cun)(cun)(cun)殘(can)跡(ji)(ji)(ji)(ji)(ji)。內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)四(si)角(jiao)(jiao)(jiao)(jiao)構筑有角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou),東(dong)北(bei)(bei)(bei)(bei)角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou)即為(wei)(wei)外(wai)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)東(dong)北(bei)(bei)(bei)(bei)角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou)。現存(cun)(cun)(cun)東(dong)南(nan)(nan)(nan)、西(xi)(xi)(xi)南(nan)(nan)(nan)角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou),尤以東(dong)南(nan)(nan)(nan)角(jiao)(jiao)(jiao)(jiao)樓(lou)(lou)較(jiao)為(wei)(wei)完整,平(ping)面近(jin)(jin)圓(yuan)形(xing),基寬(kuan)約(yue)(yue)(yue)(yue)16米(mi)(mi)(mi)(mi),高約(yue)(yue)(yue)(yue)8米(mi)(mi)(mi)(mi)。內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)未(wei)見門址與甕(weng)城(cheng)(cheng)(cheng)(cheng)(cheng)(cheng)遺(yi)跡(ji)(ji)(ji)(ji)(ji)。
外(wai)城(cheng)(cheng)地表遺物(wu)(wu)(wu)豐富(fu),尤以(yi)外(wai)城(cheng)(cheng)南側近河一帶遺物(wu)(wu)(wu)更為豐富(fu)。內(nei)城(cheng)(cheng)遺物(wu)(wu)(wu)則(ze)非常零(ling)星(xing),僅(jin)見少量細泥質(zhi)灰(hui)陶(tao)(tao)片和(he)白瓷(ci)片,以(yi)及青磚和(he)布紋瓦殘(can)片。外(wai)城(cheng)(cheng)遺物(wu)(wu)(wu)以(yi)陶(tao)(tao)、瓷(ci)器(qi)(qi)為主。陶(tao)(tao)器(qi)(qi)以(yi)泥質(zhi)灰(hui)陶(tao)(tao)為主,均輪(lun)制,火候較(jiao)高、陶(tao)(tao)質(zhi)堅硬。器(qi)(qi)形(xing)包括罐、甕、盆、壺等(deng)。陶(tao)(tao)器(qi)(qi)紋飾多樣,以(yi)多種形(xing)式的(de)附加堆(dui)紋為主,還(huan)可(ke)見篦齒紋、卷云(yun)紋等(deng)。另有少量的(de)夾砂陶(tao)(tao),主要出于(yu)城(cheng)(cheng)外(wai)南側,器(qi)(qi)形(xing)多較(jiao)小,可(ke)能為青銅時代(dai)遺物(wu)(wu)(wu)。城(cheng)(cheng)內(nei)出土(tu)瓷(ci)器(qi)(qi)均為白瓷(ci),胎質(zhi)粗糙,釉(you)色泛(fan)黃,器(qi)(qi)形(xing)有碗、盤(pan)、碟等(deng)。
城(cheng)址(zhi)(zhi)雖未發掘,城(cheng)址(zhi)(zhi)的年代、性質(zhi)認定尚無充分證據,但城(cheng)內出土遺(yi)物(wu)的特點表面,遺(yi)物(wu)多(duo)為遼金時(shi)期(qi)。《遼史(shi)》信州(zhou)條(tiao)下(xia)記錄信州(zhou)轄(xia)(xia)三(san)州(zhou)、二縣(xian)(xian)。五家子城(cheng)址(zhi)(zhi)周(zhou)長近3000米,具(ju)有(you)州(zhou)治規模(mo),可能(neng)為遼信州(zhou)下(xia)轄(xia)(xia)之州(zhou)、縣(xian)(xian)城(cheng)。對(dui)研究當時(shi)的政治、經(jing)濟、軍事、文(wen)化、交(jiao)通等(deng)各方(fang)面都具(ju)有(you)較高的歷史(shi)價值。