羅門發表於七七年的長詩「時空奏鳴曲－遙望廣九鐵路」，呈現了臺灣開放大陸探親之前，放逐者的懷鄉意識。本文即在探討此意識所投射的不同空間：被迫離開的田園故土、不得不屈身的都市叢林、以及詩詞寫意的自然風光。此時此景的缺憾，不斷將放逐者的意識帶往已成追憶的過往或者歸鄉遙不可及的未來。意識跨越的空間始自地理政治的場域，終於自然、文學的書寫天地。空間的多重變貌，反映／應了家在何處的質問，也觸及了以家為原點的身份認同的追尋。詩中的放逐者既無法認同落腳的臺北，也無法認同不同於中日、國共戰亂之前的大陸。本文的重點不僅是思鄉懷舊的情懷，也是放逐者因此情懷，不同於當地人的觀照：臺北的都市生活以及大陸的現狀，都在「過去」的映照下，透露令人省思的一面。而這種蘊藏洞見的視野，卻來自「置身事外」的疏離感。它將放逐者的意識導向社會現實之外，最後遁入書寫中的自然山水。

This paper dwells upon nostalgia as the site for preserving while refiguring the changing space of homeland to highlight the complex of Taiwanese/Chinese identity. How forceful is the impact of displacement from the Mainland China on mapping the/a homeland? What is consequently the effect on the (dis) location in Taiwan? More importantly, why does the construction of self-identity always take place within the parameter of home? This paper is an attempt to answer these questions by exploring the self that drifts in the multiple and interrelated bounds of space, from temporal horizon, through geopolitical reality and natural landscape, to poetic language. The way the poet narrates the speaker's nostalgia is discussed in terms of the spatial coordinates－namely, the past memory and the present reality, the country and the city, the inside and the outside of the self. The speaker's shifting perspective across the space of nostaligia forms, then, the basis to examine the transformation of Taiwanese/Chinese identities in exile.