1970年(nian),懷德(de)縣文(wen)化部(bu)門對境內的(de)(de)遺址(zhi)進行(xing)了(le)全面的(de)(de)普(pu)查(cha),在城址(zhi)內采集(ji)、征集(ji)各(ge)類文(wen)物(wu)數十(shi)件。1983、2009年(nian),通過第(di)二次、第(di)三次全國文(wen)物(wu)普(pu)查(cha),對城址(zhi)進行(xing)了(le)系統(tong)的(de)(de)調查(cha)和著錄(lu)。
五家(jia)子(zi)城址周(zhou)長近3000米(mi),具有州(zhou)治規模,可能(neng)為遼信州(zhou)下轄之(zhi)州(zhou)、縣(xian)城。
城(cheng)(cheng)(cheng)(cheng)址分為內、外二城(cheng)(cheng)(cheng)(cheng),城(cheng)(cheng)(cheng)(cheng)垣(yuan)均夯土構(gou)筑(zhu)。外城(cheng)(cheng)(cheng)(cheng)大致呈南(nan)(nan)(nan)(nan)北(bei)(bei)向的長(chang)方(fang)形,東(dong)(dong)(dong)、西(xi)兩(liang)(liang)墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)823米(mi),南(nan)(nan)(nan)(nan)、北(bei)(bei)兩(liang)(liang)墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)609.5米(mi),周(zhou)長(chang)約(yue)(yue)2865米(mi)。外城(cheng)(cheng)(cheng)(cheng)殘(can)(can)(can)損嚴重(zhong),城(cheng)(cheng)(cheng)(cheng)垣(yuan)基本(ben)無存,是否存有(you)馬面(mian)、甕(weng)門(men)等遺跡(ji)已不得而知。外城(cheng)(cheng)(cheng)(cheng)四角(jiao)(jiao)建有(you)角(jiao)(jiao)樓,東(dong)(dong)(dong)北(bei)(bei)角(jiao)(jiao)樓現(xian)(xian)存好,平面(mian)近(jin)(jin)圓形,直徑約(yue)(yue)12米(mi),殘(can)(can)(can)高約(yue)(yue)2米(mi),其(qi)(qi)余3處(chu)角(jiao)(jiao)樓地(di)(di)表(biao)僅見(jian)稍高于(yu)(yu)地(di)(di)表(biao)的殘(can)(can)(can)跡(ji)。外城(cheng)(cheng)(cheng)(cheng)東(dong)(dong)(dong)墻(qiang)(qiang)(qiang)位(wei)置(zhi),距內城(cheng)(cheng)(cheng)(cheng)南(nan)(nan)(nan)(nan)墻(qiang)(qiang)(qiang)約(yue)(yue)30米(mi)處(chu),現(xian)(xian)存一高約(yue)(yue)6米(mi)的圓形臺基,疑為外城(cheng)(cheng)(cheng)(cheng)東(dong)(dong)(dong)墻(qiang)(qiang)(qiang)甕(weng)門(men)的殘(can)(can)(can)跡(ji)。城(cheng)(cheng)(cheng)(cheng)外10米(mi)處(chu),東(dong)(dong)(dong)、西(xi)、北(bei)(bei)三面(mian)可(ke)見(jian)護城(cheng)(cheng)(cheng)(cheng)壕遺跡(ji),唯東(dong)(dong)(dong)城(cheng)(cheng)(cheng)(cheng)不見(jian)城(cheng)(cheng)(cheng)(cheng)壕跡(ji)象,內城(cheng)(cheng)(cheng)(cheng)位(wei)于(yu)(yu)外城(cheng)(cheng)(cheng)(cheng)的東(dong)(dong)(dong)北(bei)(bei)角(jiao)(jiao),東(dong)(dong)(dong)、北(bei)(bei)兩(liang)(liang)墻(qiang)(qiang)(qiang)借用外城(cheng)(cheng)(cheng)(cheng)的東(dong)(dong)(dong)、北(bei)(bei)二墻(qiang)(qiang)(qiang),另筑(zhu)西(xi)墻(qiang)(qiang)(qiang)和南(nan)(nan)(nan)(nan)墻(qiang)(qiang)(qiang)而成。內城(cheng)(cheng)(cheng)(cheng)平面(mian)近(jin)(jin)正方(fang)形,東(dong)(dong)(dong)、西(xi)兩(liang)(liang)墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)341米(mi),南(nan)(nan)(nan)(nan)、北(bei)(bei)兩(liang)(liang)墻(qiang)(qiang)(qiang)長(chang)約(yue)(yue)320.5米(mi),周(zhou)長(chang)約(yue)(yue)1323米(mi)。其(qi)(qi)中南(nan)(nan)(nan)(nan)墻(qiang)(qiang)(qiang)保(bao)存好,基寬約(yue)(yue)8米(mi),現(xian)(xian)高5~6米(mi),其(qi)(qi)余3面(mian)墻(qiang)(qiang)(qiang)體地(di)(di)表(biao)多僅存殘(can)(can)(can)跡(ji)。內城(cheng)(cheng)(cheng)(cheng)四角(jiao)(jiao)構(gou)筑(zhu)有(you)角(jiao)(jiao)樓,東(dong)(dong)(dong)北(bei)(bei)角(jiao)(jiao)樓即為外城(cheng)(cheng)(cheng)(cheng)東(dong)(dong)(dong)北(bei)(bei)角(jiao)(jiao)樓。現(xian)(xian)存東(dong)(dong)(dong)南(nan)(nan)(nan)(nan)、西(xi)南(nan)(nan)(nan)(nan)角(jiao)(jiao)樓,尤以(yi)東(dong)(dong)(dong)南(nan)(nan)(nan)(nan)角(jiao)(jiao)樓較為完整,平面(mian)近(jin)(jin)圓形,基寬約(yue)(yue)16米(mi),高約(yue)(yue)8米(mi)。內城(cheng)(cheng)(cheng)(cheng)未(wei)見(jian)門(men)址與甕(weng)城(cheng)(cheng)(cheng)(cheng)遺跡(ji)。
外(wai)城(cheng)(cheng)地表遺物(wu)(wu)(wu)豐富(fu),尤(you)以外(wai)城(cheng)(cheng)南(nan)側(ce)近河一帶遺物(wu)(wu)(wu)更(geng)為(wei)豐富(fu)。內(nei)城(cheng)(cheng)遺物(wu)(wu)(wu)則(ze)非常零星,僅見(jian)少(shao)量細泥(ni)質(zhi)灰陶(tao)(tao)片(pian)和白(bai)瓷(ci)片(pian),以及青(qing)磚和布紋(wen)瓦殘片(pian)。外(wai)城(cheng)(cheng)遺物(wu)(wu)(wu)以陶(tao)(tao)、瓷(ci)器(qi)(qi)為(wei)主。陶(tao)(tao)器(qi)(qi)以泥(ni)質(zhi)灰陶(tao)(tao)為(wei)主,均輪(lun)制,火候較高、陶(tao)(tao)質(zhi)堅硬。器(qi)(qi)形包括罐、甕(weng)、盆、壺等。陶(tao)(tao)器(qi)(qi)紋(wen)飾(shi)多(duo)樣,以多(duo)種形式的附(fu)加堆紋(wen)為(wei)主,還可(ke)見(jian)篦齒紋(wen)、卷云紋(wen)等。另有少(shao)量的夾砂陶(tao)(tao),主要出于城(cheng)(cheng)外(wai)南(nan)側(ce),器(qi)(qi)形多(duo)較小,可(ke)能(neng)為(wei)青(qing)銅時代遺物(wu)(wu)(wu)。城(cheng)(cheng)內(nei)出土瓷(ci)器(qi)(qi)均為(wei)白(bai)瓷(ci),胎質(zhi)粗糙(cao),釉色(se)泛黃,器(qi)(qi)形有碗、盤、碟等。
城(cheng)址雖未發(fa)掘(jue),城(cheng)址的(de)年代(dai)、性質認定尚(shang)無充分證(zheng)據,但城(cheng)內出(chu)土遺物的(de)特點表(biao)面,遺物多為(wei)遼金時期。《遼史》信(xin)州(zhou)條(tiao)下記錄信(xin)州(zhou)轄(xia)三(san)州(zhou)、二縣。五家子城(cheng)址周長近3000米,具(ju)有州(zhou)治(zhi)(zhi)規(gui)模,可能為(wei)遼信(xin)州(zhou)下轄(xia)之州(zhou)、縣城(cheng)。對研究(jiu)當時的(de)政治(zhi)(zhi)、經濟、軍事、文化、交通等各方面都具(ju)有較高(gao)的(de)歷史價值。