1937年,日人鳥山喜(xi)一(yi)、藤田(tian)亮策等對八連(lian)城(cheng)進行了調查,并對八連(lian)城(cheng)內城(cheng)宮殿址進行了盜掘。
中華人民共(gong)和國成立以后,吉(ji)林省各級(ji)文物(wu)管理(li)部(bu)門對(dui)城址開展(zhan)了多次調(diao)查(cha)和著(zhu)錄工作。
2004至(zhi)2008年(nian),吉(ji)林省(sheng)文物(wu)考(kao)古研究(jiu)所(suo)、吉(ji)林大學(xue)、琿春市(shi)文物(wu)管理(li)所(suo)等單位,對城址(zhi)進行(xing)了主動發(fa)掘。主要(yao)清理(li)了一、二號(hao)宮殿基址(zhi)及(ji)其附屬建筑遺跡,城門址(zhi)等。出土大量磚(zhuan)、瓦類建筑構件。
經考古發掘(jue)確認的(de)(de)城(cheng)(cheng)(cheng)門(men)(men)(men)有兩(liang)(liang)處(chu),分(fen)別為(wei)外城(cheng)(cheng)(cheng)南(nan)(nan)門(men)(men)(men)址和(he)內城(cheng)(cheng)(cheng)南(nan)(nan)門(men)(men)(men)址。外城(cheng)(cheng)(cheng)南(nan)(nan)門(men)(men)(men)址規模(mo)較小,單(dan)門(men)(men)(men)道,東(dong)西寬(kuan)約3.2、南(nan)(nan)北(bei)長(chang)約5.2米(mi),直接(jie)利用(yong)城(cheng)(cheng)(cheng)墻(qiang)墻(qiang)體作為(wei)城(cheng)(cheng)(cheng)門(men)(men)(men)兩(liang)(liang)側的(de)(de)墩臺。內城(cheng)(cheng)(cheng)南(nan)(nan)門(men)(men)(men)為(wei)建(jian)(jian)有夯土(tu)臺基(ji)的(de)(de)地面建(jian)(jian)筑。臺基(ji)呈長(chang)方形,南(nan)(nan)北(bei)寬(kuan)16.2米(mi),東(dong)西長(chang)27.4~28.6米(mi),東(dong)西兩(liang)(liang)端正中與城(cheng)(cheng)(cheng)墻(qiang)相(xiang)接(jie),現高0.6~0.8米(mi)。臺基(ji)上可(ke)見面闊五間,進深二間的(de)(de)圓形柱(zhu)礎(chu)基(ji)礎(chu)。臺基(ji)南(nan)(nan)、北(bei)兩(liang)(liang)側各有三(san)條兩(liang)(liang)兩(liang)(liang)相(xiang)對,以(yi)黃色夯土(tu)構筑的(de)(de)踏道。
內城的(de)縱向(xiang)中(zhong)軸(zhou)線(xian)上,有(you)(you)2座宮(gong)殿址(zhi)(zhi),分別為一(yi)、二號(hao)宮(gong)殿址(zhi)(zhi),兩(liang)(liang)座宮(gong)殿址(zhi)(zhi)兩(liang)(liang)側(ce)均有(you)(you)附(fu)屬建筑,東西兩(liang)(liang)端各與一(yi)條南北向(xiang)長廊(lang)相接,兩(liang)(liang)殿址(zhi)(zhi)間有(you)(you)一(yi)“十”字形建筑臺基建筑。
城內出(chu)(chu)土遺(yi)物以建筑構(gou)件(jian)為(wei)(wei)(wei)主,包括板(ban)瓦(wa)、筒瓦(wa)、瓦(wa)當、獸頭(tou)、套獸、鴟(chi)尾、柱圍(wei)等。瓦(wa)件(jian)多(duo)為(wei)(wei)(wei)青(qing)灰(hui)色(se),但仍不乏(fa)為(wei)(wei)(wei)數不少(shao)的黃、綠釉琉璃瓦(wa)件(jian),瓦(wa)當當面(mian)紋飾以六瓣(ban)(ban)和八(ba)瓣(ban)(ban)蓮花(hua)紋為(wei)(wei)(wei)主,另見(jian)有花(hua)草文(wen)、乳丁紋等。出(chu)(chu)土的瓦(wa)件(jian)中有相當一部分瓦(wa)身凸面(mian)帶有文(wen)字,或戳印、或刻畫,陰文(wen)、陽(yang)文(wen)均(jun)有,多(duo)數為(wei)(wei)(wei)漢字,少(shao)量為(wei)(wei)(wei)刻畫符號,累計出(chu)(chu)土九(jiu)十余(yu)種。
該城的布(bu)局與渤海上京、中京相仿,均效仿于唐長安(an)城,具有重要的歷史價值。
從城址規模(mo)、布局(ju)、主體建(jian)筑形式設計等方面比較,八連城城址與渤(bo)海(hai)中京顯德府(fu)城址(和龍(long)西(xi)古城)極(ji)為(wei)相似。這兩座城址的(de)發掘,為(wei)渤(bo)海(hai)及東北亞都城研(yan)究(jiu)提供(gong)了重要的(de)考古學資(zi)料。
渤(bo)海(hai)國城(cheng)(cheng)(cheng)(cheng)址。位(wei)于琿春市(shi)(shi)國營良種場內(nei),東(dong)(dong)距琿春市(shi)(shi)6公(gong)里,北(bei)l公(gong)里是圖(們)琿(春)公(gong)路。城(cheng)(cheng)(cheng)(cheng)址由內(nei)外兩城(cheng)(cheng)(cheng)(cheng)組(zu)成。外城(cheng)(cheng)(cheng)(cheng)平面略呈方形,城(cheng)(cheng)(cheng)(cheng)墻(qiang)土筑。周長(chang)2894米(mi),北(bei)墻(qiang)712米(mi),南墻(qiang)701米(mi),東(dong)(dong)墻(qiang)746米(mi),西(xi)墻(qiang)735米(mi)。城(cheng)(cheng)(cheng)(cheng)有(you)4門,分(fen)別(bie)(bie)設置于各墻(qiang)的中(zhong)(zhong)(zhong)部(bu),城(cheng)(cheng)(cheng)(cheng)墻(qiang)外6米(mi)處(chu)有(you)護城(cheng)(cheng)(cheng)(cheng)河遺(yi)跡。內(nei)城(cheng)(cheng)(cheng)(cheng)平面呈長(chang)方形,周長(chang)l072米(mi),南、北(bei)墻(qiang)各長(chang)218米(mi),東(dong)(dong)、西(xi)墻(qiang)各長(chang)3l8米(mi),有(you)城(cheng)(cheng)(cheng)(cheng)門3處(chu),分(fen)別(bie)(bie)修建于南、東(dong)(dong)、西(xi)墻(qiang)的中(zhong)(zhong)(zhong)部(bu)。內(nei)城(cheng)(cheng)(cheng)(cheng)中(zhong)(zhong)(zhong)央有(you)一(yi)宮殿址臺基,臺基北(bei)另有(you)殿址3處(chu)。出土文(wen)(wen)物有(you)蓮花(hua)紋瓦(wa)當、“文(wen)(wen)字”瓦(wa)、浮雕式(shi)牡丹紋和忍冬(dong)紋磚、綠釉琉璃瓦(wa)等。八(ba)(ba)連(lian)城(cheng)(cheng)(cheng)(cheng)是唐代渤(bo)海(hai)國東(dong)(dong)京(jing)龍(long)原府(fu)(fu)遺(yi)址,始建于唐德宗貞(zhen)元(yuan)元(yuan)年(785)左(zuo)右。唐貞(zhen)元(yuan)時,渤(bo)海(hai)第三代王大欽茂(mao)將其(qi)國都從上京(jing)龍(long)泉府(fu)(fu)遷至八(ba)(ba)連(lian)城(cheng)(cheng)(cheng)(cheng),唐貞(zhen)元(yuan)10年(794年),渤(bo)海(hai)成王復(fu)遷上京(jing)后,八(ba)(ba)連(lian)城(cheng)(cheng)(cheng)(cheng),仍(reng)為(wei)渤(bo)海(hai)之東(dong)(dong)京(jing)。公(gong)元(yuan)926年,遼滅渤(bo)海(hai),八(ba)(ba)連(lian)城(cheng)(cheng)(cheng)(cheng)遂(sui)廢。古城(cheng)(cheng)(cheng)(cheng)內(nei)現已辟為(wei)農田。
1961年(nian)吉林(lin)省人(ren)民委員會公布(bu)為吉林(lin)省重點文物保護單位。
2001年(nian)6月25日國務院公布(bu)為全(quan)國重點文物保護(hu)單位。